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

server/routes/federation.js

@@ -5,6 +5,7 @@ import { getDb } from '../config/database.js';
 import { authenticateToken } from '../middleware/auth.js';
 import { sendFederationInviteEmail, sendCalendarEventDeletedEmail } from '../config/mailer.js';
 import { log } from '../config/logger.js';
+import { createNotification } from '../config/notifications.js';
 
 // M13: rate limit the unauthenticated federation receive endpoint
 const federationReceiveLimiter = rateLimit({
@@ -233,6 +234,15 @@ router.post('/receive', federationReceiveLimiter, async (req, res) => {
           });
         }
 
+        // In-app notification
+        await createNotification(
+          targetUser.id,
+          'federation_invite_received',
+          from_user,
+          room_name,
+          '/federation/inbox',
+        );
+
         res.json({ success: true });
     } catch (err) {
         log.federation.error('Federation receive error:', err);