From e384ae1037ab76c648a5f588f7d7a120e45320da Mon Sep 17 00:00:00 2001
From: Ulas <ulas@kalayci.cloud>
Date: Wed, 15 Apr 2026 11:40:24 +0200
Subject: [PATCH] feat: add reminders for tasks and calendar events (closes
 #13)

- DB migration #8: reminders table (entity_type, entity_id, remind_at, dismissed, created_by)
- REST API: GET /pending, GET /?entity, POST /, PATCH /:id/dismiss, DELETE
- Client polling module (reminders.js): 60s interval, toast + Browser Notification API
- Tasks: enable reminder with custom date/time in edit modal
- Calendar: reminder offset selector (at time / 15min / 1h / 1d before)
- Bell badge shows pending count; reminders auto-dismiss after 30s or on user action
- SW shell cache updated to include reminders.js + reminders.css
- 11 new DB tests covering CRUD, pending query, dismiss, upsert, cascade delete, constraints
---
 CHANGELOG.md                |  13 ++
 package.json                |   5 +-
 public/index.html           |   1 +
 public/locales/de.json      |  21 +++
 public/locales/en.json      |  21 +++
 public/pages/calendar.js    |  86 +++++++++++-
 public/pages/tasks.js       |  99 ++++++++++++--
 public/reminders.js         | 257 ++++++++++++++++++++++++++++++++++++
 public/router.js            |   4 +
 public/styles/reminders.css |  96 ++++++++++++++
 public/sw.js                |   4 +-
 server/db-schema-test.js    |  14 ++
 server/db.js                |  19 +++
 server/index.js             |   2 +
 server/routes/reminders.js  | 210 +++++++++++++++++++++++++++++
 test-reminders.js           | 229 ++++++++++++++++++++++++++++++++
 16 files changed, 1061 insertions(+), 20 deletions(-)
 create mode 100644 public/reminders.js
 create mode 100644 public/styles/reminders.css
 create mode 100644 server/routes/reminders.js
 create mode 100644 test-reminders.js

diff --git a/CHANGELOG.md b/CHANGELOG.md
index d527ab2..ea578df 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,6 +7,19 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+## [0.20.0] - 2026-04-15
+
+### Added
+- Reminders: set time-based reminders on tasks and calendar events (closes #13)
+  - Tasks: enable a reminder with a custom date and time via the task edit modal
+  - Calendar events: choose an offset (at time, 15 min, 1 hour, or 1 day before) via the event edit dialog
+  - In-app toast notifications (built via DOM API, no external dependencies) appear when a reminder is due
+  - Browser Notification API support - reminders fire as system notifications when permission is granted
+  - Client-side polling every 60 seconds checks for pending reminders
+  - Reminders can be dismissed individually; dismissed reminders no longer appear
+  - Bell badge on each reminder shows pending count when reminders are due
+  - DB migration #8 adds `reminders` table with `entity_type`, `entity_id`, `remind_at`, `dismissed` fields and appropriate indexes
+
 ## [0.19.6] - 2026-04-15
 
 ### Added
diff --git a/package.json b/package.json
index ec531a8..d5bcadd 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "oikos",
-  "version": "0.19.6",
+  "version": "0.20.0",
   "description": "Self-hosted family planner - calendar, tasks, shopping, meal planning, budget and more. Private, open-source, no subscription.",
   "main": "server/index.js",
   "type": "module",
@@ -20,7 +20,8 @@
     "test:ncb": "node --experimental-sqlite test-notes-contacts-budget.js",
     "test:ux-utils": "node test-ux-utils.js",
     "test:modal-utils": "node --loader ./test-browser-loader.mjs test-modal-utils.js",
-    "test": "node --experimental-sqlite test-db.js && node --experimental-sqlite test-dashboard.js && node --experimental-sqlite test-tasks.js && node --experimental-sqlite test-shopping.js && node --experimental-sqlite test-meals.js && node --experimental-sqlite test-calendar.js && node --experimental-sqlite test-notes-contacts-budget.js && npm run test:ux-utils && npm run test:modal-utils"
+    "test:reminders": "node --experimental-sqlite test-reminders.js",
+    "test": "node --experimental-sqlite test-db.js && node --experimental-sqlite test-dashboard.js && node --experimental-sqlite test-tasks.js && node --experimental-sqlite test-shopping.js && node --experimental-sqlite test-meals.js && node --experimental-sqlite test-calendar.js && node --experimental-sqlite test-notes-contacts-budget.js && npm run test:ux-utils && npm run test:modal-utils && npm run test:reminders"
   },
   "dependencies": {
     "bcrypt": "^6.0.0",
diff --git a/public/index.html b/public/index.html
index 311bcd1..b8b4f43 100644
--- a/public/index.html
+++ b/public/index.html
@@ -38,6 +38,7 @@
   <link rel="stylesheet" href="/styles/layout.css" />
   <link rel="stylesheet" href="/styles/glass.css" />
   <link rel="stylesheet" href="/styles/login.css" />
+  <link rel="stylesheet" href="/styles/reminders.css" />
 
   <!-- Theme: Vor CSS-Rendering anwenden (Flash-Prevention) -->
   <script>
diff --git a/public/locales/de.json b/public/locales/de.json
index 94470bd..3c4c5aa 100644
--- a/public/locales/de.json
+++ b/public/locales/de.json
@@ -597,5 +597,26 @@
     "unitWeeks": "Wochen",
     "unitMonth": "Monat",
     "unitMonths": "Monate"
+  },
+  "reminders": {
+    "sectionTitle": "Erinnerung",
+    "enableLabel": "Erinnerung setzen",
+    "dateLabel": "Datum",
+    "timeLabel": "Uhrzeit",
+    "offsetLabel": "Erinnern",
+    "offsetNone": "Keine",
+    "offset15min": "15 Minuten vorher",
+    "offset1hour": "1 Stunde vorher",
+    "offset1day": "1 Tag vorher",
+    "offsetAtTime": "Zum Startzeitpunkt",
+    "toastTitle": "Erinnerung",
+    "dismiss": "Verwerfen",
+    "notificationPermission": "Browser-Benachrichtigungen",
+    "notificationEnable": "Benachrichtigungen aktivieren",
+    "notificationEnabled": "Benachrichtigungen aktiv",
+    "notificationDenied": "Benachrichtigungen blockiert",
+    "notificationHint": "Erhalte Benachrichtigungen auch wenn die App geöffnet ist.",
+    "pendingBadgeTitle": "{{count}} fällige Erinnerung",
+    "pendingBadgeTitlePlural": "{{count}} fällige Erinnerungen"
   }
 }
\ No newline at end of file
diff --git a/public/locales/en.json b/public/locales/en.json
index 21e257f..f123d64 100644
--- a/public/locales/en.json
+++ b/public/locales/en.json
@@ -597,5 +597,26 @@
     "unitWeeks": "weeks",
     "unitMonth": "month",
     "unitMonths": "months"
+  },
+  "reminders": {
+    "sectionTitle": "Reminder",
+    "enableLabel": "Set reminder",
+    "dateLabel": "Date",
+    "timeLabel": "Time",
+    "offsetLabel": "Remind me",
+    "offsetNone": "None",
+    "offset15min": "15 minutes before",
+    "offset1hour": "1 hour before",
+    "offset1day": "1 day before",
+    "offsetAtTime": "At event time",
+    "toastTitle": "Reminder",
+    "dismiss": "Dismiss",
+    "notificationPermission": "Browser notifications",
+    "notificationEnable": "Enable notifications",
+    "notificationEnabled": "Notifications active",
+    "notificationDenied": "Notifications blocked",
+    "notificationHint": "Receive notifications while the app is open.",
+    "pendingBadgeTitle": "{{count}} reminder due",
+    "pendingBadgeTitlePlural": "{{count}} reminders due"
   }
 }
\ No newline at end of file
diff --git a/public/pages/calendar.js b/public/pages/calendar.js
index 72fb040..193a054 100644
--- a/public/pages/calendar.js
+++ b/public/pages/calendar.js
@@ -10,6 +10,7 @@ import { openModal as openSharedModal, closeModal, confirmModal } from '/compone
 import { stagger } from '/utils/ux.js';
 import { t, formatTime } from '/i18n.js';
 import { esc } from '/utils/html.js';
+import { refresh as refreshReminders } from '/reminders.js';
 
 // --------------------------------------------------------
 // Konstanten
@@ -695,9 +696,10 @@ function showEventPopup(ev, anchor) {
   popup.style.top  = `${Math.max(8, top)}px`;
   popup.style.left = `${Math.max(8, left)}px`;
 
-  popup.querySelector('#popup-edit').addEventListener('click', () => {
+  popup.querySelector('#popup-edit').addEventListener('click', async () => {
     popup.remove();
-    openEventModal({ mode: 'edit', event: ev });
+    const reminder = await loadReminderForEvent(ev.id);
+    openEventModal({ mode: 'edit', event: ev, reminder });
   });
 
   popup.querySelector('#popup-delete').addEventListener('click', async () => {
@@ -717,13 +719,59 @@ function showEventPopup(ev, anchor) {
   }, 0);
 }
 
+// --------------------------------------------------------
+// Reminder-Helfer für Kalender-Events
+// --------------------------------------------------------
+
+async function loadReminderForEvent(eventId) {
+  try {
+    const data = await api.get(`/reminders?entity_type=event&entity_id=${eventId}`);
+    return data.data;
+  } catch {
+    return null;
+  }
+}
+
+const REMINDER_OFFSETS = () => [
+  { value: '',     label: t('reminders.offsetNone')   },
+  { value: '0',    label: t('reminders.offsetAtTime') },
+  { value: '15',   label: t('reminders.offset15min')  },
+  { value: '60',   label: t('reminders.offset1hour')  },
+  { value: '1440', label: t('reminders.offset1day')   },
+];
+
+function reminderOffsetFromEvent(event, reminder) {
+  if (!reminder || !event?.start_datetime) return '';
+  const remindMs = new Date(reminder.remind_at).getTime();
+  const startMs  = new Date(event.start_datetime).getTime();
+  const diffMin  = Math.round((startMs - remindMs) / 60000);
+  const opts = [0, 15, 60, 1440];
+  const match = opts.find((o) => o === diffMin);
+  return match !== undefined ? String(match) : '';
+}
+
+function renderCalendarReminderSection(reminder = null, event = null) {
+  const currentOffset = event ? reminderOffsetFromEvent(event, reminder) : '';
+  return `
+    <div class="reminder-section">
+      <div class="form-group" style="margin:0">
+        <label class="form-label" for="modal-reminder-offset">${t('reminders.offsetLabel')}</label>
+        <select class="form-input" id="modal-reminder-offset" style="min-height:44px">
+          ${REMINDER_OFFSETS().map((o) =>
+            `<option value="${o.value}" ${currentOffset === o.value ? 'selected' : ''}>${esc(o.label)}</option>`
+          ).join('')}
+        </select>
+      </div>
+    </div>`;
+}
+
 // --------------------------------------------------------
 // Event-Modal (Erstellen / Bearbeiten)
 // --------------------------------------------------------
 
-function openEventModal({ mode, event = null, date = null }) {
+function openEventModal({ mode, event = null, date = null, reminder = null }) {
   const isEdit = mode === 'edit';
-  const content = buildEventModalContent({ mode, event, date });
+  const content = buildEventModalContent({ mode, event, date, reminder });
 
   openSharedModal({
     title: isEdit ? t('calendar.editEvent') : t('calendar.newEvent'),
@@ -764,12 +812,12 @@ function openEventModal({ mode, event = null, date = null }) {
         await deleteEvent(event.id);
       });
 
-      panel.querySelector('#modal-save').addEventListener('click', () => saveEvent(panel, mode, event?.id));
+      panel.querySelector('#modal-save').addEventListener('click', () => saveEvent(panel, mode, event?.id, reminder));
     },
   });
 }
 
-function buildEventModalContent({ mode, event, date }) {
+function buildEventModalContent({ mode, event, date, reminder = null }) {
   const isEdit = mode === 'edit';
   const today  = date || state.today;
 
@@ -867,6 +915,8 @@ function buildEventModalContent({ mode, event, date }) {
 
     ${renderRRuleFields('event', isEdit ? event.recurrence_rule : null)}
 
+    ${renderCalendarReminderSection(reminder, event)}
+
     <div class="modal-panel__footer" style="border:none;padding:0;margin-top:var(--space-4)">
       ${isEdit ? `<button class="btn btn--danger btn--icon" id="modal-delete" aria-label="${t('calendar.deleteEvent')}">
         <i data-lucide="trash-2" style="width:16px;height:16px;" aria-hidden="true"></i>
@@ -878,7 +928,7 @@ function buildEventModalContent({ mode, event, date }) {
     </div>`;
 }
 
-async function saveEvent(overlay, mode, eventId) {
+async function saveEvent(overlay, mode, eventId, existingReminder = null) {
   const saveBtn = overlay.querySelector('#modal-save');
   const title   = overlay.querySelector('#modal-title').value.trim();
 
@@ -922,15 +972,35 @@ async function saveEvent(overlay, mode, eventId) {
       recurrence_rule: rrule.recurrence_rule,
     };
 
+    let savedEventId = eventId;
     if (mode === 'create') {
       const res = await api.post('/calendar', body);
       state.events.push(res.data);
+      savedEventId = res.data?.id;
     } else {
       const res = await api.put(`/calendar/${eventId}`, body);
       const idx = state.events.findIndex((e) => e.id === eventId);
       if (idx !== -1) state.events[idx] = res.data;
     }
 
+    // Erinnerung speichern oder löschen
+    if (savedEventId) {
+      const offsetSel = overlay.querySelector('#modal-reminder-offset');
+      const offsetVal = offsetSel?.value;
+
+      if (offsetVal !== '' && offsetVal !== undefined) {
+        // Remind-Zeitpunkt = start_datetime - offset (in Minuten)
+        const startMs  = new Date(start_datetime).getTime();
+        const offsetMs = parseInt(offsetVal, 10) * 60000;
+        const remindAt = new Date(startMs - offsetMs).toISOString().slice(0, 16);
+        await api.post('/reminders', { entity_type: 'event', entity_id: savedEventId, remind_at: remindAt });
+        refreshReminders();
+      } else {
+        api.delete(`/reminders?entity_type=event&entity_id=${savedEventId}`).catch(() => {});
+        refreshReminders();
+      }
+    }
+
     closeModal();
     renderView();
     window.oikos?.showToast(mode === 'create' ? t('calendar.createdToast') : t('calendar.savedToast'), 'success');
@@ -944,6 +1014,8 @@ async function saveEvent(overlay, mode, eventId) {
 async function deleteEvent(id) {
   try {
     await api.delete(`/calendar/${id}`);
+    api.delete(`/reminders?entity_type=event&entity_id=${id}`).catch(() => {});
+    refreshReminders();
     state.events = state.events.filter((e) => e.id !== id);
     renderView();
     window.oikos?.showToast(t('calendar.deletedToast'), 'success');
diff --git a/public/pages/tasks.js b/public/pages/tasks.js
index 6575170..e76c08b 100644
--- a/public/pages/tasks.js
+++ b/public/pages/tasks.js
@@ -10,6 +10,7 @@ import { openModal as openSharedModal, closeModal, wireBlurValidation, validateA
 import { stagger, vibrate } from '/utils/ux.js';
 import { t, formatDate } from '/i18n.js';
 import { esc } from '/utils/html.js';
+import { refresh as refreshReminders } from '/reminders.js';
 
 // --------------------------------------------------------
 // Konstanten
@@ -243,7 +244,7 @@ function renderTaskGroups(tasks, groupMode) {
 // Task-Modal (Erstellen / Bearbeiten)
 // --------------------------------------------------------
 
-function renderModalContent({ task = null, users = [] } = {}) {
+function renderModalContent({ task = null, users = [], reminder = null } = {}) {
   const isEdit = !!task;
 
   const userOptions = users.map((u) =>
@@ -334,6 +335,8 @@ function renderModalContent({ task = null, users = [] } = {}) {
 
       ${renderRRuleFields('task', task?.recurrence_rule)}
 
+      ${renderReminderSection(reminder)}
+
       <div id="task-form-error" class="login-error" hidden></div>
 
       <div class="modal-panel__footer" style="padding:0;border:none;margin-top:var(--space-6)">
@@ -392,15 +395,51 @@ async function loadTaskForEdit(id) {
   return data.data;
 }
 
+async function loadReminderForTask(taskId) {
+  try {
+    const data = await api.get(`/reminders?entity_type=task&entity_id=${taskId}`);
+    return data.data;
+  } catch {
+    return null;
+  }
+}
+
+function renderReminderSection(reminder = null) {
+  const hasReminder  = !!reminder;
+  const remindDate   = hasReminder ? reminder.remind_at.slice(0, 10) : '';
+  const remindTime   = hasReminder ? reminder.remind_at.slice(11, 16) : '';
+
+  return `
+    <div class="reminder-section">
+      <div class="reminder-section__header">
+        <label class="toggle" style="margin:0">
+          <input type="checkbox" id="reminder-toggle" ${hasReminder ? 'checked' : ''}>
+          <span class="toggle__track"></span>
+          <span class="reminder-section__title">${t('reminders.enableLabel')}</span>
+        </label>
+      </div>
+      <div id="reminder-fields" class="reminder-fields" ${hasReminder ? '' : 'style="display:none"'}>
+        <div class="form-group" style="margin:0">
+          <label class="label" for="reminder-date">${t('reminders.dateLabel')}</label>
+          <input class="input" type="date" id="reminder-date" value="${remindDate}">
+        </div>
+        <div class="form-group" style="margin:0">
+          <label class="label" for="reminder-time">${t('reminders.timeLabel')}</label>
+          <input class="input" type="time" id="reminder-time" value="${remindTime || '08:00'}">
+        </div>
+      </div>
+    </div>`;
+}
+
 // --------------------------------------------------------
 // Modal-Verwaltung (delegiert an Shared Modal-System)
 // --------------------------------------------------------
 
-function openTaskModal({ task = null, users = [] } = {}, container) {
+function openTaskModal({ task = null, users = [], reminder = null } = {}, container) {
   const isEdit = !!task;
   openSharedModal({
     title: isEdit ? t('tasks.editTask') : t('tasks.newTask'),
-    content: renderModalContent({ task, users }),
+    content: renderModalContent({ task, users, reminder }),
     size: 'lg',
     onSave(panel) {
       // RRULE-Events binden
@@ -409,6 +448,13 @@ function openTaskModal({ task = null, users = [] } = {}, container) {
       // Blur-Validierung für required-Felder aktivieren
       wireBlurValidation(panel);
 
+      // Reminder-Toggle: Felder ein-/ausblenden
+      const toggle = panel.querySelector('#reminder-toggle');
+      const fields = panel.querySelector('#reminder-fields');
+      toggle?.addEventListener('change', () => {
+        fields.style.display = toggle.checked ? '' : 'none';
+      });
+
       // Form-Events
       panel.querySelector('#task-form')
         ?.addEventListener('submit', (e) => handleFormSubmit(e, container));
@@ -454,13 +500,34 @@ async function handleFormSubmit(e, container) {
   if (form.status) body.status = form.status.value;
 
   try {
+    let savedTaskId = taskId;
     if (taskId) {
       await api.put(`/tasks/${taskId}`, body);
       window.oikos.showToast(t('tasks.savedToast'), 'success');
     } else {
-      await api.post('/tasks', body);
+      const res = await api.post('/tasks', body);
+      savedTaskId = res.data?.id;
       window.oikos.showToast(t('tasks.createdToast'), 'success');
     }
+
+    // Erinnerung speichern oder löschen
+    if (savedTaskId) {
+      const reminderToggle = form.querySelector('#reminder-toggle');
+      const reminderDate   = form.querySelector('#reminder-date')?.value;
+      const reminderTime   = form.querySelector('#reminder-time')?.value || '08:00';
+
+      if (reminderToggle?.checked && reminderDate) {
+        const remindAt = `${reminderDate}T${reminderTime}`;
+        await api.post('/reminders', { entity_type: 'task', entity_id: savedTaskId, remind_at: remindAt });
+        refreshReminders();
+      } else if (!reminderToggle?.checked) {
+        try {
+          await api.delete(`/reminders?entity_type=task&entity_id=${savedTaskId}`);
+          refreshReminders();
+        } catch { /* kein Reminder vorhanden - ignorieren */ }
+      }
+    }
+
     btnSuccess(submitBtn, originalLabel);
     setTimeout(() => closeModal(), 700);
     await loadTasks(container);
@@ -477,6 +544,9 @@ async function handleDeleteTask(id, container) {
   if (!await confirmModal(t('tasks.deleteConfirm'), { danger: true, confirmLabel: t('common.delete') })) return;
   try {
     await api.delete(`/tasks/${id}`);
+    // Erinnerungen für diese Aufgabe ebenfalls entfernen
+    api.delete(`/reminders?entity_type=task&entity_id=${id}`).catch(() => {});
+    refreshReminders();
     closeModal();
     window.oikos.showToast(t('tasks.deletedToast'), 'default');
     await loadTasks(container);
@@ -670,8 +740,11 @@ function wireKanbanDrag(container) {
       const card = e.target.closest('.kanban-card[data-task-id]');
       if (!card) return;
       try {
-        const task = await loadTaskForEdit(card.dataset.taskId);
-        openTaskModal({ task, users: state.users }, container);
+        const [task, reminder] = await Promise.all([
+          loadTaskForEdit(card.dataset.taskId),
+          loadReminderForTask(card.dataset.taskId),
+        ]);
+        openTaskModal({ task, users: state.users, reminder }, container);
       } catch (err) {
         window.oikos.showToast(t('tasks.loadError'), 'danger');
       }
@@ -880,8 +953,11 @@ function wireSwipeGestures(container) {
         resetCard(true);
         vibrate(20);
         try {
-          const task = await loadTaskForEdit(taskId);
-          openTaskModal({ task, users: state.users }, container);
+          const [task, reminder] = await Promise.all([
+            loadTaskForEdit(taskId),
+            loadReminderForTask(taskId),
+          ]);
+          openTaskModal({ task, users: state.users, reminder }, container);
         } catch (err) {
           window.oikos.showToast(t('tasks.loadError'), 'danger');
         }
@@ -1013,8 +1089,11 @@ function wireTaskList(container) {
 
     if (action === 'edit-task' || action === 'open-task') {
       try {
-        const task = await loadTaskForEdit(id);
-        openTaskModal({ task, users: state.users }, container);
+        const [task, reminder] = await Promise.all([
+          loadTaskForEdit(id),
+          loadReminderForTask(id),
+        ]);
+        openTaskModal({ task, users: state.users, reminder }, container);
       } catch (err) {
         window.oikos.showToast(t('tasks.loadError'), 'danger');
       }
diff --git a/public/reminders.js b/public/reminders.js
new file mode 100644
index 0000000..660491b
--- /dev/null
+++ b/public/reminders.js
@@ -0,0 +1,257 @@
+/**
+ * Modul: Erinnerungen (Reminders)
+ * Zweck: Clientseitiges Polling für fällige Erinnerungen, Browser-Benachrichtigungen,
+ *        In-App-Toasts und Bell-Badge-Aktualisierung.
+ * Abhängigkeiten: /api.js, /i18n.js
+ */
+
+import { api } from '/api.js';
+import { t } from '/i18n.js';
+
+// --------------------------------------------------------
+// Konfiguration
+// --------------------------------------------------------
+
+const POLL_INTERVAL_MS = 60_000; // 1 Minute
+
+// --------------------------------------------------------
+// Zustand
+// --------------------------------------------------------
+
+let _pollTimer     = null;
+let _shownIds      = new Set(); // bereits angezeigte Reminder-IDs in dieser Session
+let _isInitialized = false;
+
+// --------------------------------------------------------
+// Browser-Benachrichtigungen
+// --------------------------------------------------------
+
+/**
+ * Aktuellen Benachrichtigungs-Permission-Status zurückgeben.
+ * @returns {'granted'|'denied'|'default'|'unsupported'}
+ */
+function notificationStatus() {
+  if (!('Notification' in window)) return 'unsupported';
+  return Notification.permission;
+}
+
+/**
+ * Browser-Benachrichtigung anfordern.
+ * @returns {Promise<'granted'|'denied'|'default'>}
+ */
+async function requestPermission() {
+  if (!('Notification' in window)) return 'unsupported';
+  if (Notification.permission === 'granted') return 'granted';
+  return Notification.requestPermission();
+}
+
+/**
+ * Zeigt eine native Browser-Benachrichtigung an.
+ * @param {string} title
+ * @param {string} body
+ */
+function showBrowserNotification(title, body) {
+  if (!('Notification' in window) || Notification.permission !== 'granted') return;
+  try {
+    const n = new Notification(title, { body, icon: '/icons/icon-192.png' });
+    setTimeout(() => n.close(), 8000);
+  } catch {
+    // Notification-API kann in bestimmten Kontexten fehlschlagen
+  }
+}
+
+// --------------------------------------------------------
+// Bell-Badge (Sidebar / Bottom-Nav)
+// --------------------------------------------------------
+
+/**
+ * Aktualisiert den Badge-Zähler am Bell-Icon in der Navigation.
+ * @param {number} count
+ */
+function updateBellBadge(count) {
+  document.querySelectorAll('.reminder-bell-badge').forEach((badge) => {
+    if (count > 0) {
+      badge.textContent = count > 9 ? '9+' : String(count);
+      badge.hidden = false;
+    } else {
+      badge.hidden = true;
+    }
+  });
+}
+
+// --------------------------------------------------------
+// SVG-Helfer (DOM-API, kein innerHTML)
+// --------------------------------------------------------
+
+function createBellSvg() {
+  const NS  = 'http://www.w3.org/2000/svg';
+  const svg = document.createElementNS(NS, 'svg');
+  svg.setAttribute('viewBox', '0 0 24 24');
+  svg.setAttribute('fill', 'none');
+  svg.setAttribute('stroke', 'currentColor');
+  svg.setAttribute('stroke-width', '2');
+  svg.setAttribute('width', '16');
+  svg.setAttribute('height', '16');
+  svg.setAttribute('aria-hidden', 'true');
+
+  const path1 = document.createElementNS(NS, 'path');
+  path1.setAttribute('d', 'M18 8A6 6 0 0 0 6 8c0 7-3 9-3 9h18s-3-2-3-9');
+  const path2 = document.createElementNS(NS, 'path');
+  path2.setAttribute('d', 'M13.73 21a2 2 0 0 1-3.46 0');
+
+  svg.appendChild(path1);
+  svg.appendChild(path2);
+  return svg;
+}
+
+// --------------------------------------------------------
+// Erinnerungen anzeigen
+// --------------------------------------------------------
+
+/**
+ * Verarbeitet eine Liste fälliger Erinnerungen und zeigt Toast + Browser-Notification.
+ * @param {Array} reminders
+ */
+function processReminders(reminders) {
+  const newOnes = reminders.filter((r) => !_shownIds.has(r.id));
+  if (!newOnes.length) return;
+
+  newOnes.forEach((reminder) => {
+    _shownIds.add(reminder.id);
+    showReminderToast(reminder);
+    showBrowserNotification(
+      t('reminders.toastTitle'),
+      reminder.entity_title || ''
+    );
+  });
+}
+
+/**
+ * Zeigt einen persistenten Toast für eine Erinnerung mit Verwerfen-Button.
+ * @param {{ id: number, entity_title: string }} reminder
+ */
+function showReminderToast(reminder) {
+  const container = document.getElementById('toast-container');
+  if (!container) return;
+
+  const existing = container.querySelectorAll('.toast');
+  if (existing.length >= 3) existing[0].remove();
+
+  const toast = document.createElement('div');
+  toast.className = 'toast toast--reminder';
+  toast.setAttribute('role', 'alert');
+  toast.dataset.reminderId = reminder.id;
+
+  const iconWrap = document.createElement('span');
+  iconWrap.className = 'toast__reminder-icon';
+  iconWrap.setAttribute('aria-hidden', 'true');
+  iconWrap.appendChild(createBellSvg());
+
+  const textSpan = document.createElement('span');
+  textSpan.className = 'toast__reminder-text';
+
+  const titleEl = document.createElement('strong');
+  titleEl.textContent = t('reminders.toastTitle');
+
+  const sep = document.createTextNode(': ');
+
+  const bodyEl = document.createElement('span');
+  bodyEl.textContent = reminder.entity_title || '';
+
+  textSpan.appendChild(titleEl);
+  textSpan.appendChild(sep);
+  textSpan.appendChild(bodyEl);
+
+  const dismissBtn = document.createElement('button');
+  dismissBtn.className = 'toast__undo';
+  dismissBtn.textContent = t('reminders.dismiss');
+  dismissBtn.addEventListener('click', () => {
+    dismissReminder(reminder.id);
+    toast.remove();
+  });
+
+  toast.appendChild(iconWrap);
+  toast.appendChild(textSpan);
+  toast.appendChild(dismissBtn);
+  container.appendChild(toast);
+
+  // Reminder-Toasts bleiben 30 Sekunden sichtbar
+  const dismissTimer = setTimeout(() => {
+    toast.classList.add('toast--out');
+    toast.addEventListener('animationend', () => toast.remove(), { once: true });
+  }, 30_000);
+
+  toast.addEventListener('click', (e) => {
+    if (e.target === dismissBtn) return;
+    clearTimeout(dismissTimer);
+    dismissReminder(reminder.id);
+    toast.remove();
+  });
+}
+
+// --------------------------------------------------------
+// API-Aktionen
+// --------------------------------------------------------
+
+/**
+ * Verwirft eine Erinnerung serverseitig.
+ * @param {number} id
+ */
+async function dismissReminder(id) {
+  try {
+    await api.patch(`/reminders/${id}/dismiss`, {});
+    _shownIds.delete(id);
+  } catch {
+    // Netzwerkfehler ignorieren
+  }
+}
+
+/**
+ * Lädt fällige Erinnerungen vom Server und verarbeitet sie.
+ */
+async function poll() {
+  try {
+    const data = await api.get('/reminders/pending');
+    const reminders = data.data ?? [];
+    updateBellBadge(reminders.length);
+    processReminders(reminders);
+  } catch {
+    // Polling-Fehler ignorieren (kann Offline-Zustand sein)
+  }
+}
+
+// --------------------------------------------------------
+// Öffentliche API
+// --------------------------------------------------------
+
+/**
+ * Startet das Reminder-Polling. Idempotent.
+ */
+function init() {
+  if (_isInitialized) return;
+  _isInitialized = true;
+  poll();
+  _pollTimer = setInterval(poll, POLL_INTERVAL_MS);
+}
+
+/**
+ * Stoppt das Polling (z.B. nach Logout).
+ */
+function stop() {
+  if (_pollTimer) {
+    clearInterval(_pollTimer);
+    _pollTimer = null;
+  }
+  _isInitialized = false;
+  _shownIds.clear();
+  updateBellBadge(0);
+}
+
+/**
+ * Erzwingt sofortigen Poll (z.B. nach Erstellen einer Erinnerung).
+ */
+function refresh() {
+  poll();
+}
+
+export { init, stop, refresh, requestPermission, notificationStatus };
diff --git a/public/router.js b/public/router.js
index 16903a6..d1d1ce7 100644
--- a/public/router.js
+++ b/public/router.js
@@ -6,6 +6,7 @@
 
 import { auth } from '/api.js';
 import { initI18n, getLocale, t } from '/i18n.js';
+import { init as initReminders, stop as stopReminders } from '/reminders.js';
 
 // --------------------------------------------------------
 // Routen-Definitionen
@@ -144,6 +145,7 @@ async function navigate(path, userOrPushState = true, pushState = true) {
     // Überlastung: navigate(path, user) nach Login vs navigate(path, false) beim Init
     if (typeof userOrPushState === 'object' && userOrPushState !== null) {
       currentUser = userOrPushState;
+      initReminders();
     } else {
       pushState = userOrPushState;
     }
@@ -159,6 +161,7 @@ async function navigate(path, userOrPushState = true, pushState = true) {
       try {
         const result = await auth.me();
         currentUser = result.user;
+        initReminders();
       } catch {
         currentPath = null; // Reset damit navigate('/login') nicht geblockt wird
         isNavigating = false;
@@ -507,6 +510,7 @@ window.addEventListener('popstate', (e) => {
 // Session abgelaufen
 window.addEventListener('auth:expired', () => {
   currentUser = null;
+  stopReminders();
   navigate('/login');
 });
 
diff --git a/public/styles/reminders.css b/public/styles/reminders.css
new file mode 100644
index 0000000..78eea76
--- /dev/null
+++ b/public/styles/reminders.css
@@ -0,0 +1,96 @@
+/* --------------------------------------------------------
+   Modul: Erinnerungen (Reminders)
+   Zweck: Bell-Badge in der Navigation, Reminder-Toast-Styling
+   -------------------------------------------------------- */
+
+/* Bell-Badge: Rote Zahl über dem Bell-Icon */
+.nav-item--reminder {
+  position: relative;
+}
+
+.reminder-bell-badge {
+  position: absolute;
+  top: 2px;
+  right: 2px;
+  min-width: 16px;
+  height: 16px;
+  padding: 0 4px;
+  border-radius: var(--radius-full, 9999px);
+  background: var(--color-priority-urgent, #EF4444);
+  color: #fff;
+  font-size: 10px;
+  font-weight: 700;
+  line-height: 16px;
+  text-align: center;
+  pointer-events: none;
+  z-index: 1;
+}
+
+/* Reminder-Toast: Bell-Icon + Textblock */
+.toast--reminder {
+  gap: var(--space-2, 8px);
+  cursor: pointer;
+  padding-right: var(--space-2, 8px);
+}
+
+.toast__reminder-icon {
+  display: flex;
+  align-items: center;
+  flex-shrink: 0;
+  color: var(--color-accent, #2563EB);
+}
+
+.toast__reminder-text {
+  display: flex;
+  flex-direction: column;
+  flex: 1;
+  gap: 2px;
+  min-width: 0;
+}
+
+.toast__reminder-text strong {
+  font-size: var(--text-xs, 0.75rem);
+  text-transform: uppercase;
+  letter-spacing: 0.05em;
+  opacity: 0.7;
+}
+
+.toast__reminder-text span {
+  font-size: var(--text-sm, 0.875rem);
+  font-weight: 500;
+  overflow: hidden;
+  text-overflow: ellipsis;
+  white-space: nowrap;
+}
+
+/* Reminder-Abschnitt in Modals */
+.reminder-section {
+  border-top: 1px solid var(--color-border, rgba(0,0,0,0.1));
+  padding-top: var(--space-4, 16px);
+  margin-top: var(--space-4, 16px);
+}
+
+.reminder-section__header {
+  display: flex;
+  align-items: center;
+  gap: var(--space-2, 8px);
+  margin-bottom: var(--space-3, 12px);
+}
+
+.reminder-section__title {
+  font-size: var(--text-sm, 0.875rem);
+  font-weight: 600;
+  color: var(--color-text-primary);
+}
+
+.reminder-fields {
+  display: grid;
+  grid-template-columns: 1fr 1fr;
+  gap: var(--space-3, 12px);
+}
+
+@media (max-width: 480px) {
+  .reminder-fields {
+    grid-template-columns: 1fr;
+  }
+}
diff --git a/public/sw.js b/public/sw.js
index 648375b..57da731 100644
--- a/public/sw.js
+++ b/public/sw.js
@@ -12,7 +12,7 @@
  *   API: Immer Netzwerk (kein Caching von Nutzerdaten)
  */
 
-const SHELL_CACHE   = 'oikos-shell-v31';
+const SHELL_CACHE   = 'oikos-shell-v32';
 const PAGES_CACHE   = 'oikos-pages-v28';
 const ASSETS_CACHE  = 'oikos-assets-v27';
 const ALL_CACHES    = [SHELL_CACHE, PAGES_CACHE, ASSETS_CACHE];
@@ -31,6 +31,7 @@ const APP_SHELL = [
   '/locales/ar.json',
   '/locales/hi.json',
   '/locales/pt.json',
+  '/reminders.js',
   '/sw-register.js',
   '/lucide.min.js',
   '/styles/tokens.css',
@@ -39,6 +40,7 @@ const APP_SHELL = [
   '/styles/layout.css',
   '/styles/glass.css',
   '/styles/login.css',
+  '/styles/reminders.css',
   '/styles/dashboard.css',
   '/styles/tasks.css',
   '/styles/shopping.css',
diff --git a/server/db-schema-test.js b/server/db-schema-test.js
index 8c7f008..5dc436b 100644
--- a/server/db-schema-test.js
+++ b/server/db-schema-test.js
@@ -178,6 +178,20 @@ const MIGRATIONS_SQL = {
     );
     CREATE INDEX IF NOT EXISTS idx_calendar_external_id ON calendar_events(external_calendar_id);
   `,
+  8: `
+    CREATE TABLE IF NOT EXISTS reminders (
+      id          INTEGER PRIMARY KEY AUTOINCREMENT,
+      entity_type TEXT    NOT NULL CHECK(entity_type IN ('task', 'event')),
+      entity_id   INTEGER NOT NULL,
+      remind_at   TEXT    NOT NULL,
+      dismissed   INTEGER NOT NULL DEFAULT 0,
+      created_by  INTEGER NOT NULL REFERENCES users(id) ON DELETE CASCADE,
+      created_at  TEXT    NOT NULL DEFAULT (strftime('%Y-%m-%dT%H:%M:%SZ', 'now'))
+    );
+    CREATE INDEX IF NOT EXISTS idx_reminders_entity ON reminders(entity_type, entity_id);
+    CREATE INDEX IF NOT EXISTS idx_reminders_remind ON reminders(remind_at);
+    CREATE INDEX IF NOT EXISTS idx_reminders_user   ON reminders(created_by);
+  `,
 };
 
 export { MIGRATIONS_SQL };
diff --git a/server/db.js b/server/db.js
index 2060b18..9443dbc 100644
--- a/server/db.js
+++ b/server/db.js
@@ -369,6 +369,25 @@ const MIGRATIONS = [
       ALTER TABLE meal_ingredients ADD COLUMN category TEXT NOT NULL DEFAULT 'Sonstiges';
     `,
   },
+  {
+    version: 8,
+    description: 'Erinnerungen (Reminders) für Aufgaben und Kalender-Events',
+    up: `
+      CREATE TABLE IF NOT EXISTS reminders (
+        id          INTEGER PRIMARY KEY AUTOINCREMENT,
+        entity_type TEXT    NOT NULL CHECK(entity_type IN ('task', 'event')),
+        entity_id   INTEGER NOT NULL,
+        remind_at   TEXT    NOT NULL,
+        dismissed   INTEGER NOT NULL DEFAULT 0,
+        created_by  INTEGER NOT NULL REFERENCES users(id) ON DELETE CASCADE,
+        created_at  TEXT    NOT NULL DEFAULT (strftime('%Y-%m-%dT%H:%M:%SZ', 'now'))
+      );
+
+      CREATE INDEX IF NOT EXISTS idx_reminders_entity ON reminders(entity_type, entity_id);
+      CREATE INDEX IF NOT EXISTS idx_reminders_remind ON reminders(remind_at);
+      CREATE INDEX IF NOT EXISTS idx_reminders_user   ON reminders(created_by);
+    `,
+  },
 ];
 
 /**
diff --git a/server/index.js b/server/index.js
index 5f8e0c9..b971b17 100644
--- a/server/index.js
+++ b/server/index.js
@@ -24,6 +24,7 @@ import contactsRouter from './routes/contacts.js';
 import budgetRouter from './routes/budget.js';
 import weatherRouter from './routes/weather.js';
 import preferencesRouter from './routes/preferences.js';
+import remindersRouter from './routes/reminders.js';
 
 const log     = createLogger('Server');
 const logSync = createLogger('Sync');
@@ -165,6 +166,7 @@ app.use('/api/v1/contacts', contactsRouter);
 app.use('/api/v1/budget', budgetRouter);
 app.use('/api/v1/weather', weatherRouter);
 app.use('/api/v1/preferences', preferencesRouter);
+app.use('/api/v1/reminders', remindersRouter);
 
 // --------------------------------------------------------
 // Health-Check (für Docker)
diff --git a/server/routes/reminders.js b/server/routes/reminders.js
new file mode 100644
index 0000000..00de8bc
--- /dev/null
+++ b/server/routes/reminders.js
@@ -0,0 +1,210 @@
+/**
+ * Modul: Erinnerungen (Reminders)
+ * Zweck: REST-API für Erinnerungen an Aufgaben und Kalender-Events
+ * Abhängigkeiten: express, server/db.js
+ */
+
+import { createLogger } from '../logger.js';
+import express from 'express';
+import * as db from '../db.js';
+import * as v from '../middleware/validate.js';
+
+const log    = createLogger('Reminders');
+const router = express.Router();
+
+const VALID_ENTITY_TYPES = ['task', 'event'];
+
+// --------------------------------------------------------
+// GET /api/v1/reminders/pending
+// Gibt alle fälligen, nicht-verworfenen Erinnerungen des aktuellen Nutzers zurück.
+// "Fällig" = remind_at <= jetzt
+// Response: { data: Reminder[] }
+// --------------------------------------------------------
+router.get('/pending', (req, res) => {
+  try {
+    const userId = req.session.userId;
+    const now    = new Date().toISOString();
+
+    const rows = db.get().prepare(`
+      SELECT
+        r.*,
+        CASE r.entity_type
+          WHEN 'task'  THEN (SELECT title FROM tasks           WHERE id = r.entity_id)
+          WHEN 'event' THEN (SELECT title FROM calendar_events WHERE id = r.entity_id)
+        END AS entity_title
+      FROM reminders r
+      WHERE r.created_by  = ?
+        AND r.dismissed   = 0
+        AND r.remind_at  <= ?
+      ORDER BY r.remind_at ASC
+    `).all(userId, now);
+
+    res.json({ data: rows });
+  } catch (err) {
+    log.error('Fehler beim Laden fälliger Erinnerungen:', err.message);
+    res.status(500).json({ error: 'Interner Fehler.', code: 500 });
+  }
+});
+
+// --------------------------------------------------------
+// GET /api/v1/reminders?entity_type=task&entity_id=5
+// Gibt die Erinnerung für eine spezifische Entität zurück (oder null).
+// Response: { data: Reminder | null }
+// --------------------------------------------------------
+router.get('/', (req, res) => {
+  try {
+    const userId      = req.session.userId;
+    const entityType  = req.query.entity_type;
+    const entityId    = parseInt(req.query.entity_id, 10);
+
+    if (!VALID_ENTITY_TYPES.includes(entityType) || !entityId) {
+      return res.status(400).json({ error: 'entity_type und entity_id sind erforderlich.', code: 400 });
+    }
+
+    const row = db.get().prepare(`
+      SELECT * FROM reminders
+      WHERE entity_type = ? AND entity_id = ? AND created_by = ? AND dismissed = 0
+      ORDER BY created_at DESC LIMIT 1
+    `).get(entityType, entityId, userId);
+
+    res.json({ data: row || null });
+  } catch (err) {
+    log.error('Fehler beim Laden der Erinnerung:', err.message);
+    res.status(500).json({ error: 'Interner Fehler.', code: 500 });
+  }
+});
+
+// --------------------------------------------------------
+// POST /api/v1/reminders
+// Erstellt oder ersetzt die Erinnerung für eine Entität.
+// Body: { entity_type, entity_id, remind_at }
+// Response: { data: Reminder }
+// --------------------------------------------------------
+router.post('/', (req, res) => {
+  try {
+    const userId = req.session.userId;
+    const { entity_type, entity_id, remind_at } = req.body;
+
+    const errors = v.collectErrors([
+      v.oneOf(entity_type,     VALID_ENTITY_TYPES, 'entity_type'),
+      v.id(entity_id,          'entity_id'),
+      v.datetime(remind_at,    'remind_at', true),
+    ]);
+
+    if (!entity_type || !VALID_ENTITY_TYPES.includes(entity_type)) {
+      errors.push('entity_type muss "task" oder "event" sein.');
+    }
+
+    if (errors.length) {
+      return res.status(400).json({ error: errors.join(' '), code: 400 });
+    }
+
+    const entityId = parseInt(entity_id, 10);
+
+    // Bestehende nicht-verworfene Erinnerungen für diese Entität löschen
+    db.get().prepare(`
+      DELETE FROM reminders
+      WHERE entity_type = ? AND entity_id = ? AND created_by = ?
+    `).run(entity_type, entityId, userId);
+
+    const result = db.get().prepare(`
+      INSERT INTO reminders (entity_type, entity_id, remind_at, created_by)
+      VALUES (?, ?, ?, ?)
+    `).run(entity_type, entityId, remind_at, userId);
+
+    const row = db.get().prepare('SELECT * FROM reminders WHERE id = ?').get(result.lastInsertRowid);
+    res.status(201).json({ data: row });
+  } catch (err) {
+    log.error('Fehler beim Erstellen der Erinnerung:', err.message);
+    res.status(500).json({ error: 'Interner Fehler.', code: 500 });
+  }
+});
+
+// --------------------------------------------------------
+// PATCH /api/v1/reminders/:id/dismiss
+// Markiert eine Erinnerung als verworfen.
+// Response: { data: { id } }
+// --------------------------------------------------------
+router.patch('/:id/dismiss', (req, res) => {
+  try {
+    const userId     = req.session.userId;
+    const reminderId = parseInt(req.params.id, 10);
+
+    if (!reminderId) {
+      return res.status(400).json({ error: 'Ungültige Erinnerungs-ID.', code: 400 });
+    }
+
+    const reminder = db.get().prepare(
+      'SELECT * FROM reminders WHERE id = ? AND created_by = ?'
+    ).get(reminderId, userId);
+
+    if (!reminder) {
+      return res.status(404).json({ error: 'Erinnerung nicht gefunden.', code: 404 });
+    }
+
+    db.get().prepare('UPDATE reminders SET dismissed = 1 WHERE id = ?').run(reminderId);
+    res.json({ data: { id: reminderId } });
+  } catch (err) {
+    log.error('Fehler beim Verwerfen der Erinnerung:', err.message);
+    res.status(500).json({ error: 'Interner Fehler.', code: 500 });
+  }
+});
+
+// --------------------------------------------------------
+// DELETE /api/v1/reminders/:id
+// Löscht eine Erinnerung dauerhaft.
+// Response: 204 No Content
+// --------------------------------------------------------
+router.delete('/:id', (req, res) => {
+  try {
+    const userId     = req.session.userId;
+    const reminderId = parseInt(req.params.id, 10);
+
+    if (!reminderId) {
+      return res.status(400).json({ error: 'Ungültige Erinnerungs-ID.', code: 400 });
+    }
+
+    const reminder = db.get().prepare(
+      'SELECT id FROM reminders WHERE id = ? AND created_by = ?'
+    ).get(reminderId, userId);
+
+    if (!reminder) {
+      return res.status(404).json({ error: 'Erinnerung nicht gefunden.', code: 404 });
+    }
+
+    db.get().prepare('DELETE FROM reminders WHERE id = ?').run(reminderId);
+    res.status(204).end();
+  } catch (err) {
+    log.error('Fehler beim Löschen der Erinnerung:', err.message);
+    res.status(500).json({ error: 'Interner Fehler.', code: 500 });
+  }
+});
+
+// --------------------------------------------------------
+// DELETE /api/v1/reminders?entity_type=task&entity_id=5
+// Löscht alle Erinnerungen für eine Entität (z.B. bei Task-Löschung).
+// Response: 204 No Content
+// --------------------------------------------------------
+router.delete('/', (req, res) => {
+  try {
+    const userId     = req.session.userId;
+    const entityType = req.query.entity_type;
+    const entityId   = parseInt(req.query.entity_id, 10);
+
+    if (!VALID_ENTITY_TYPES.includes(entityType) || !entityId) {
+      return res.status(400).json({ error: 'entity_type und entity_id sind erforderlich.', code: 400 });
+    }
+
+    db.get().prepare(`
+      DELETE FROM reminders
+      WHERE entity_type = ? AND entity_id = ? AND created_by = ?
+    `).run(entityType, entityId, userId);
+
+    res.status(204).end();
+  } catch (err) {
+    log.error('Fehler beim Löschen der Erinnerungen:', err.message);
+    res.status(500).json({ error: 'Interner Fehler.', code: 500 });
+  }
+});
+
+export default router;
diff --git a/test-reminders.js b/test-reminders.js
new file mode 100644
index 0000000..9f462ca
--- /dev/null
+++ b/test-reminders.js
@@ -0,0 +1,229 @@
+/**
+ * Modul: Reminders-Test
+ * Zweck: Validiert DB-Schema und Abfragen für Erinnerungen
+ * Ausführen: node --experimental-sqlite test-reminders.js
+ */
+
+import { DatabaseSync } from 'node:sqlite';
+
+let passed = 0;
+let failed = 0;
+
+function test(name, fn) {
+  try { fn(); console.log(`  ✓ ${name}`); passed++; }
+  catch (err) { console.error(`  ✗ ${name}: ${err.message}`); failed++; }
+}
+function assert(cond, msg) { if (!cond) throw new Error(msg || 'Assertion fehlgeschlagen'); }
+
+// Hilfsfunktion: SQL-Block in Einzelstatements aufteilen und ausführen
+function runSQL(database, sqlBlock) {
+  const statements = sqlBlock.split(';').map((s) => s.trim()).filter(Boolean);
+  for (const stmt of statements) {
+    database.prepare(stmt).run();
+  }
+}
+
+const db = new DatabaseSync(':memory:');
+db.exec('PRAGMA foreign_keys = ON;');
+
+// Minimales Schema aufbauen: users + calendar_events + reminders
+runSQL(db, `
+  CREATE TABLE IF NOT EXISTS users (
+    id            INTEGER PRIMARY KEY AUTOINCREMENT,
+    username      TEXT    UNIQUE NOT NULL,
+    display_name  TEXT    NOT NULL,
+    password_hash TEXT    NOT NULL,
+    avatar_color  TEXT    NOT NULL DEFAULT '#007AFF',
+    role          TEXT    NOT NULL DEFAULT 'member',
+    created_at    TEXT    NOT NULL DEFAULT (strftime('%Y-%m-%dT%H:%M:%SZ', 'now')),
+    updated_at    TEXT    NOT NULL DEFAULT (strftime('%Y-%m-%dT%H:%M:%SZ', 'now'))
+  )
+`);
+
+runSQL(db, `
+  CREATE TABLE IF NOT EXISTS tasks (
+    id         INTEGER PRIMARY KEY AUTOINCREMENT,
+    title      TEXT    NOT NULL,
+    category   TEXT    NOT NULL DEFAULT 'Sonstiges',
+    status     TEXT    NOT NULL DEFAULT 'open',
+    created_by INTEGER NOT NULL REFERENCES users(id) ON DELETE CASCADE
+  )
+`);
+
+runSQL(db, `
+  CREATE TABLE IF NOT EXISTS calendar_events (
+    id               INTEGER PRIMARY KEY AUTOINCREMENT,
+    title            TEXT    NOT NULL,
+    start_datetime   TEXT    NOT NULL,
+    created_by       INTEGER NOT NULL REFERENCES users(id) ON DELETE CASCADE,
+    external_source  TEXT    NOT NULL DEFAULT 'local'
+  )
+`);
+
+runSQL(db, `
+  CREATE TABLE IF NOT EXISTS reminders (
+    id          INTEGER PRIMARY KEY AUTOINCREMENT,
+    entity_type TEXT    NOT NULL CHECK(entity_type IN ('task', 'event')),
+    entity_id   INTEGER NOT NULL,
+    remind_at   TEXT    NOT NULL,
+    dismissed   INTEGER NOT NULL DEFAULT 0,
+    created_by  INTEGER NOT NULL REFERENCES users(id) ON DELETE CASCADE,
+    created_at  TEXT    NOT NULL DEFAULT (strftime('%Y-%m-%dT%H:%M:%SZ', 'now'))
+  )
+`);
+
+runSQL(db, `
+  CREATE INDEX IF NOT EXISTS idx_reminders_entity ON reminders(entity_type, entity_id)
+`);
+
+runSQL(db, `
+  CREATE INDEX IF NOT EXISTS idx_reminders_remind ON reminders(remind_at)
+`);
+
+runSQL(db, `
+  CREATE INDEX IF NOT EXISTS idx_reminders_user ON reminders(created_by)
+`);
+
+// Testdaten anlegen
+const u1    = db.prepare(`INSERT INTO users (username, display_name, password_hash, avatar_color)
+  VALUES ('admin', 'Anna', 'x', '#007AFF')`).run();
+const uid1  = u1.lastInsertRowid;
+
+const task1 = db.prepare(`INSERT INTO tasks (title, created_by) VALUES ('Steuererklärung', ?)`).run(uid1);
+const taskId = task1.lastInsertRowid;
+
+const ev1   = db.prepare(`INSERT INTO calendar_events (title, start_datetime, created_by)
+  VALUES ('Zahnarzt', '2026-05-01T10:00', ?)`).run(uid1);
+const evId  = ev1.lastInsertRowid;
+
+const now    = new Date().toISOString();
+const future = new Date(Date.now() + 3_600_000).toISOString().slice(0, 16);
+const past   = new Date(Date.now() - 3_600_000).toISOString().slice(0, 16);
+
+console.log('\n[Reminders-Test] Schema + CRUD + Pending-Abfragen\n');
+
+// --------------------------------------------------------
+// Erstellen
+// --------------------------------------------------------
+
+let reminderId1, reminderId2;
+
+test('Erinnerung für Aufgabe erstellen', () => {
+  const r = db.prepare(`INSERT INTO reminders (entity_type, entity_id, remind_at, created_by)
+    VALUES ('task', ?, ?, ?)`).run(taskId, future, uid1);
+  reminderId1 = r.lastInsertRowid;
+  assert(reminderId1 > 0, 'Keine lastInsertRowid');
+});
+
+test('Erinnerung für Event erstellen', () => {
+  const r = db.prepare(`INSERT INTO reminders (entity_type, entity_id, remind_at, created_by)
+    VALUES ('event', ?, ?, ?)`).run(evId, past, uid1);
+  reminderId2 = r.lastInsertRowid;
+  assert(reminderId2 > 0, 'Keine lastInsertRowid');
+});
+
+// --------------------------------------------------------
+// Lesen
+// --------------------------------------------------------
+
+test('Erinnerung nach entity_type + entity_id laden', () => {
+  const row = db.prepare(`SELECT * FROM reminders
+    WHERE entity_type = 'task' AND entity_id = ? AND created_by = ?`).get(taskId, uid1);
+  assert(row !== null && row !== undefined, 'Keine Zeile zurückgegeben');
+  assert(row.entity_type === 'task', 'Falscher entity_type');
+  assert(row.dismissed === 0, 'dismissed sollte 0 sein');
+});
+
+test('Pending-Abfrage liefert nur fällige (remind_at <= now)', () => {
+  const rows = db.prepare(`SELECT * FROM reminders
+    WHERE created_by = ? AND dismissed = 0 AND remind_at <= ?`).all(uid1, now);
+  assert(rows.length === 1, `Erwartet 1, erhalten ${rows.length}`);
+  assert(rows[0].entity_type === 'event', 'Falscher entity_type in Pending-Abfrage');
+});
+
+test('Zukunfts-Reminder erscheint nicht in Pending', () => {
+  const rows = db.prepare(`SELECT * FROM reminders
+    WHERE created_by = ? AND dismissed = 0 AND remind_at <= ?`).all(uid1, now);
+  const futureFound = rows.some((r) => r.id === reminderId1);
+  assert(!futureFound, 'Zukünftiger Reminder in Pending-Liste');
+});
+
+// --------------------------------------------------------
+// Verwerfen (dismiss)
+// --------------------------------------------------------
+
+test('Erinnerung verwerfen', () => {
+  db.prepare(`UPDATE reminders SET dismissed = 1 WHERE id = ?`).run(reminderId2);
+  const row = db.prepare(`SELECT dismissed FROM reminders WHERE id = ?`).get(reminderId2);
+  assert(row.dismissed === 1, 'dismissed ist nicht 1');
+});
+
+test('Verworfene Erinnerung erscheint nicht in Pending', () => {
+  const rows = db.prepare(`SELECT * FROM reminders
+    WHERE created_by = ? AND dismissed = 0 AND remind_at <= ?`).all(uid1, now);
+  assert(rows.length === 0, `Erwartet 0 nach Dismiss, erhalten ${rows.length}`);
+});
+
+// --------------------------------------------------------
+// Ersetzen (Upsert: erst löschen, dann neu einfügen)
+// --------------------------------------------------------
+
+test('Erinnerung ersetzen: alte löschen + neue einfügen', () => {
+  db.prepare(`DELETE FROM reminders WHERE entity_type = 'task' AND entity_id = ? AND created_by = ?`)
+    .run(taskId, uid1);
+  const newFuture = new Date(Date.now() + 7_200_000).toISOString().slice(0, 16);
+  db.prepare(`INSERT INTO reminders (entity_type, entity_id, remind_at, created_by)
+    VALUES ('task', ?, ?, ?)`).run(taskId, newFuture, uid1);
+
+  const rows = db.prepare(`SELECT * FROM reminders WHERE entity_type = 'task' AND entity_id = ?`)
+    .all(taskId);
+  assert(rows.length === 1, `Erwartet 1 Zeile nach Ersetzen, erhalten ${rows.length}`);
+});
+
+// --------------------------------------------------------
+// Löschen
+// --------------------------------------------------------
+
+test('Alle Erinnerungen einer Entität löschen', () => {
+  db.prepare(`DELETE FROM reminders WHERE entity_type = 'task' AND entity_id = ? AND created_by = ?`)
+    .run(taskId, uid1);
+  const rows = db.prepare(`SELECT * FROM reminders WHERE entity_type = 'task' AND entity_id = ?`)
+    .all(taskId);
+  assert(rows.length === 0, `Erwartet 0 nach Löschen, erhalten ${rows.length}`);
+});
+
+test('Nutzer-DELETE CASCADE: Erinnerungen werden mitgelöscht', () => {
+  const u2    = db.prepare(`INSERT INTO users (username, display_name, password_hash, avatar_color)
+    VALUES ('temp', 'Temp', 'x', '#FF0000')`).run();
+  const tempUid = u2.lastInsertRowid;
+
+  db.prepare(`INSERT INTO reminders (entity_type, entity_id, remind_at, created_by)
+    VALUES ('task', ?, ?, ?)`).run(taskId, future, tempUid);
+
+  db.prepare(`DELETE FROM users WHERE id = ?`).run(tempUid);
+
+  const rows = db.prepare(`SELECT * FROM reminders WHERE created_by = ?`).all(tempUid);
+  assert(rows.length === 0, 'Cascade-Delete hat nicht funktioniert');
+});
+
+// --------------------------------------------------------
+// Constraints
+// --------------------------------------------------------
+
+test('Ungültiger entity_type wird abgelehnt', () => {
+  let threw = false;
+  try {
+    db.prepare(`INSERT INTO reminders (entity_type, entity_id, remind_at, created_by)
+      VALUES ('invalid', 1, ?, ?)`).run(future, uid1);
+  } catch {
+    threw = true;
+  }
+  assert(threw, 'CHECK-Constraint hat entity_type nicht abgelehnt');
+});
+
+// --------------------------------------------------------
+// Ergebnis
+// --------------------------------------------------------
+
+console.log(`\n  ${passed} bestanden, ${failed} fehlgeschlagen\n`);
+if (failed > 0) process.exit(1);