Refresh device and notification lists on return navigation

Subscribes the devices list and notifications list to a shared
RouteObserver so they refetch when a pushed route (e.g. device detail)
is popped, avoiding stale state after registering or updating a device.

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

frontend/lib/home/notifications_list.dart

@@ -3,6 +3,7 @@ import 'dart:async';
 import 'package:flutter/material.dart';
 
 import '../model/notification.dart' as oott_model;
+import '../navigation.dart';
 import '../utils/friendly_date_formatter.dart';
 import '../utils/oott_api.dart';
 import '../utils/ui_snackbars.dart';
@@ -35,7 +36,7 @@ class NotificationsList extends StatefulWidget {
   State<NotificationsList> createState() => _NotificationsListState();
 }
 
-class _NotificationsListState extends State<NotificationsList> {
+class _NotificationsListState extends State<NotificationsList> with RouteAware {
   _NotificationFilter _filter = _NotificationFilter.newOnly;
   Timer? _notificationTimer;
 
@@ -54,8 +55,23 @@ class _NotificationsListState extends State<NotificationsList> {
     );
   }
 
+  @override
+  void didChangeDependencies() {
+    super.didChangeDependencies();
+    final route = ModalRoute.of(context);
+    if (route is ModalRoute<void>) {
+      routeObserver.subscribe(this, route);
+    }
+  }
+
+  @override
+  void didPopNext() {
+    _fetchPage(_currentPage);
+  }
+
   @override
   void dispose() {
+    routeObserver.unsubscribe(this);
     _notificationTimer?.cancel();
     super.dispose();
   }