feat(caldav): implement account CRUD operations

Add createAccount, updateAccount, deleteAccount functions with validation, error handling, and logging. Implements Task 3 from the CalDAV multi-account spec.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

server/services/caldav-sync.js

@@ -53,7 +53,108 @@ function getAllAccounts() {
 }
 
 // --------------------------------------------------------
-// Export placeholder (will be filled in next tasks)
+// Account CRUD Operations
 // --------------------------------------------------------
 
-export { };
+/**
+ * Create a new CalDAV account
+ * @param {string} label - User-friendly label
+ * @param {string} url - CalDAV server URL
+ * @param {string} username - Account username
+ * @param {string} password - Account password
+ * @returns {number} Account ID
+ */
+function createAccount(label, url, username, password) {
+  if (!label || !url || !username || !password) {
+    throw new Error('All fields required: label, url, username, password');
+  }
+
+  const result = db.get().prepare(`
+    INSERT INTO caldav_accounts (label, url, username, password)
+    VALUES (?, ?, ?, ?)
+  `).run(label, url, username, password);
+
+  log.info('CalDAV account created', { id: result.lastInsertRowid, label });
+  return result.lastInsertRowid;
+}
+
+/**
+ * Update an existing CalDAV account
+ * @param {number} accountId - Account ID
+ * @param {object} updates - Fields to update
+ * @returns {void}
+ */
+function updateAccount(accountId, updates) {
+  const account = getAccountById(accountId);
+  if (!account) {
+    throw new Error(`CalDAV account not found: ${accountId}`);
+  }
+
+  const { label, url, username, password } = updates;
+  const fields = [];
+  const values = [];
+
+  if (label !== undefined) {
+    fields.push('label = ?');
+    values.push(label);
+  }
+  if (url !== undefined) {
+    fields.push('url = ?');
+    values.push(url);
+  }
+  if (username !== undefined) {
+    fields.push('username = ?');
+    values.push(username);
+  }
+  if (password !== undefined) {
+    fields.push('password = ?');
+    values.push(password);
+  }
+
+  if (fields.length === 0) {
+    throw new Error('No fields to update');
+  }
+
+  values.push(accountId);
+
+  db.get().prepare(`
+    UPDATE caldav_accounts
+    SET ${fields.join(', ')}
+    WHERE id = ?
+  `).run(...values);
+
+  log.info('CalDAV account updated', { id: accountId, fields: Object.keys(updates) });
+}
+
+/**
+ * Delete a CalDAV account and all associated data
+ * @param {number} accountId - Account ID
+ * @returns {void}
+ */
+function deleteAccount(accountId) {
+  const account = getAccountById(accountId);
+  if (!account) {
+    throw new Error(`CalDAV account not found: ${accountId}`);
+  }
+
+  // Foreign key constraints will cascade delete:
+  // - caldav_selected_calendars
+  // - external_calendars (via source)
+  // - calendar_events (via external_calendar_id)
+
+  db.get().prepare('DELETE FROM caldav_accounts WHERE id = ?').run(accountId);
+
+  log.info('CalDAV account deleted', { id: accountId, label: account.label });
+}
+
+// --------------------------------------------------------
+// Exports
+// --------------------------------------------------------
+
+export {
+  createAccount,
+  updateAccount,
+  deleteAccount,
+  getAccountById,
+  getAllAccounts
+};