feat: FAB (Floating Action Button) auf allen Unterseiten für Mobile

- Einheitlicher blauer Plus-Button unten rechts auf Mobile (tasks, calendar,
  notes, contacts, budget) — konsistent mit Dashboard-FAB
- Toolbar-"Neu"-Buttons auf Mobile versteckt, auf Desktop weiterhin sichtbar
- Wiederverwendbare .page-fab CSS-Klasse in layout.css
- Dashboard-FAB Position an neue Nav-Höhe angepasst
- Service Worker Cache v13

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

public/pages/budget.js

@@ -98,6 +98,9 @@ export async function render(container, { user }) {
       <div id="budget-body" style="flex:1;display:flex;flex-direction:column;overflow:hidden;">
         <div style="padding:2rem;text-align:center;color:var(--color-text-disabled);">Lade…</div>
       </div>
+      <button class="page-fab" id="fab-new-budget" aria-label="Neuer Eintrag">
+        <i data-lucide="plus" style="width:24px;height:24px"></i>
+      </button>
     </div>
   `;
 
@@ -131,7 +134,9 @@ function wireNav() {
     renderBody();
     updateLabel();
   });
-  _container.querySelector('#budget-add').addEventListener('click', () => openModal({ mode: 'create' }));
+  const addHandler = () => openModal({ mode: 'create' });
+  _container.querySelector('#budget-add').addEventListener('click', addHandler);
+  _container.querySelector('#fab-new-budget').addEventListener('click', addHandler);
   updateLabel();
 }
 

public/pages/calendar.js

@@ -159,6 +159,9 @@ export async function render(container, { user }) {
     <div class="calendar-page" id="calendar-page">
       <div class="cal-toolbar" id="cal-toolbar"></div>
       <div id="cal-body" style="flex:1;display:flex;flex-direction:column;overflow:hidden;"></div>
+      <button class="page-fab" id="fab-new-event" aria-label="Neuer Termin">
+        <i data-lucide="plus" style="width:24px;height:24px"></i>
+      </button>
     </div>
   `;
 
@@ -167,6 +170,8 @@ export async function render(container, { user }) {
 
   renderToolbar();
   renderView();
+
+  container.querySelector('#fab-new-event')?.addEventListener('click', () => openEventModal({ mode: 'create' }));
 }
 
 // --------------------------------------------------------

public/pages/contacts.js

@@ -61,6 +61,9 @@ export async function render(container, { user }) {
         `).join('')}
       </div>
       <div id="contacts-list" class="contacts-list"></div>
+      <button class="page-fab" id="fab-new-contact" aria-label="Neuer Kontakt">
+        <i data-lucide="plus" style="width:24px;height:24px"></i>
+      </button>
     </div>
   `;
 
@@ -92,9 +95,9 @@ export async function render(container, { user }) {
   });
 
   // Neu
-  _container.querySelector('#contacts-add-btn').addEventListener('click', () =>
-    openModal({ mode: 'create' })
-  );
+  const addHandler = () => openModal({ mode: 'create' });
+  _container.querySelector('#contacts-add-btn').addEventListener('click', addHandler);
+  _container.querySelector('#fab-new-contact').addEventListener('click', addHandler);
 }
 
 // --------------------------------------------------------

public/pages/notes.js

@@ -53,6 +53,9 @@ export async function render(container, { user }) {
         </button>
       </div>
       <div id="notes-grid" class="notes-grid"></div>
+      <button class="page-fab" id="fab-new-note" aria-label="Neue Notiz">
+        <i data-lucide="plus" style="width:24px;height:24px"></i>
+      </button>
     </div>
   `;
 
@@ -68,7 +71,9 @@ export async function render(container, { user }) {
   }
   renderGrid();
 
-  _container.querySelector('#notes-add-btn').addEventListener('click', () => openModal({ mode: 'create' }));
+  const addHandler = () => openModal({ mode: 'create' });
+  _container.querySelector('#notes-add-btn').addEventListener('click', addHandler);
+  _container.querySelector('#fab-new-note').addEventListener('click', addHandler);
 }
 
 // --------------------------------------------------------

public/pages/tasks.js

@@ -864,10 +864,12 @@ function wireGroupToggle(container) {
 }
 
 function wireNewTaskBtn(container) {
-  container.querySelector('#btn-new-task')?.addEventListener('click', () => {
+  const handler = () => {
     openModal(renderModal({ users: state.users }));
     wireModalEvents(container);
-  });
+  };
+  container.querySelector('#btn-new-task')?.addEventListener('click', handler);
+  container.querySelector('#fab-new-task')?.addEventListener('click', handler);
 }
 
 function wireModalEvents(container) {
@@ -974,6 +976,9 @@ export async function render(container, { user }) {
             <div class="skeleton skeleton-line skeleton-line--short" style="height:12px"></div>
           </div>`).join('')}
       </div>
+      <button class="page-fab" id="fab-new-task" aria-label="Neue Aufgabe">
+        <i data-lucide="plus" style="width:24px;height:24px"></i>
+      </button>
     </div>
   `;