feat(notifications): implement notification system with CRUD operations and UI integration

server/config/notifications.js

@@ -0,0 +1,23 @@
+import { getDb } from './database.js';
+
+/**
+ * Create an in-app notification for a user.
+ * Non-fatal — exceptions are swallowed so that the main operation is never blocked.
+ *
+ * @param {number} userId   - Recipient user ID
+ * @param {string} type     - Notification type (room_share_added | room_share_removed | federation_invite_received)
+ * @param {string} title    - Short title (e.g. room name or "from" address)
+ * @param {string|null} body  - Optional longer message
+ * @param {string|null} link  - Optional frontend path to navigate to when clicked
+ */
+export async function createNotification(userId, type, title, body = null, link = null) {
+  try {
+    const db = getDb();
+    await db.run(
+      'INSERT INTO notifications (user_id, type, title, body, link) VALUES (?, ?, ?, ?, ?)',
+      [userId, type, title, body, link],
+    );
+  } catch {
+    // Notifications are non-critical — never break main functionality
+  }
+}