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

server/config/database.js

@@ -617,6 +617,38 @@ export async function initDatabase() {
     `);
   }
 
+  // ── Notifications table ──────────────────────────────────────────────────
+  if (isPostgres) {
+    await db.exec(`
+      CREATE TABLE IF NOT EXISTS notifications (
+        id SERIAL PRIMARY KEY,
+        user_id INTEGER NOT NULL REFERENCES users(id) ON DELETE CASCADE,
+        type TEXT NOT NULL,
+        title TEXT NOT NULL,
+        body TEXT,
+        link TEXT,
+        read INTEGER DEFAULT 0,
+        created_at TIMESTAMP DEFAULT NOW()
+      );
+      CREATE INDEX IF NOT EXISTS idx_notifications_user_id ON notifications(user_id);
+    `);
+  } else {
+    await db.exec(`
+      CREATE TABLE IF NOT EXISTS notifications (
+        id INTEGER PRIMARY KEY AUTOINCREMENT,
+        user_id INTEGER NOT NULL,
+        type TEXT NOT NULL,
+        title TEXT NOT NULL,
+        body TEXT,
+        link TEXT,
+        read INTEGER DEFAULT 0,
+        created_at DATETIME DEFAULT CURRENT_TIMESTAMP,
+        FOREIGN KEY (user_id) REFERENCES users(id) ON DELETE CASCADE
+      );
+      CREATE INDEX IF NOT EXISTS idx_notifications_user_id ON notifications(user_id);
+    `);
+  }
+
   // ── Default admin (only on very first start) ────────────────────────────
   const adminAlreadySeeded = await db.get("SELECT value FROM settings WHERE key = 'admin_seeded'");
   if (!adminAlreadySeeded) {

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
+  }
+}