Add pull-to-refresh to the notifications list

The devices list already supported pull-to-refresh; mirror that on the
notifications list by wrapping its CustomScrollView in a RefreshIndicator
with AlwaysScrollableScrollPhysics. Keep the existing list visible during
a refresh (_isLoading = _items.isEmpty) instead of flashing the skeleton,
matching the devices list behaviour.

Add widget tests covering pull-to-refresh for both lists.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/lib/home/notifications_list.dart

@@ -126,7 +126,7 @@ class _NotificationsListState extends State<NotificationsList>
     final token = CancelToken();
     _fetchToken = token;
     setState(() {
-      _isLoading = true;
+      _isLoading = _items.isEmpty;
       _error = null;
     });
     try {
@@ -217,12 +217,16 @@ class _NotificationsListState extends State<NotificationsList>
       children: [
         _buildNotificationsHeader(context),
         Expanded(
-          child: CustomScrollView(
-            controller: _scrollController,
-            slivers: [
-              ..._buildNotificationSlivers(context),
-              ...widget.trailingSlivers,
-            ],
+          child: RefreshIndicator(
+            onRefresh: () => _fetchPage(_currentPage),
+            child: CustomScrollView(
+              controller: _scrollController,
+              physics: const AlwaysScrollableScrollPhysics(),
+              slivers: [
+                ..._buildNotificationSlivers(context),
+                ...widget.trailingSlivers,
+              ],
+            ),
           ),
         ),
       ],

frontend/test/widget/device_list_test.dart

@@ -100,4 +100,30 @@ void main() {
 
     await tearDownTree(tester);
   });
+
+  testWidgets('pulling the list down refetches devices', (tester) async {
+    // A single reply list whose contents are swapped before the pull, so the
+    // same route re-serializes fresh data on the refresh request.
+    final devices = <Map<String, dynamic>>[
+      deviceJson(macAddress: '00:00:00:00:00:01'),
+    ];
+    adapter.onGet('/devices', (server) => server.reply(200, devices));
+
+    await pumpScreen(tester, const DeviceList());
+    await pumpUntilFound(tester, find.byType(DeviceRowWide));
+    expect(find.byType(DeviceRowWide), findsOneWidget);
+
+    // The next fetch returns an extra device; a pull-down should pick it up.
+    devices.add(deviceJson(macAddress: '00:00:00:00:00:02'));
+    await tester.fling(
+      find.byType(CustomScrollView),
+      const Offset(0, 300),
+      1000,
+    );
+    await tester.pumpAndSettle();
+
+    expect(find.byType(DeviceRowWide), findsNWidgets(2));
+
+    await tearDownTree(tester);
+  });
 }

frontend/test/widget/notifications_list_test.dart

@@ -105,4 +105,46 @@ void main() {
 
     await tester.pumpWidget(const SizedBox());
   });
+
+  testWidgets('pulling the list down refetches notifications', (tester) async {
+    tester.view.physicalSize = const Size(400, 600);
+    tester.view.devicePixelRatio = 1.0;
+    addTearDown(tester.view.resetPhysicalSize);
+
+    // A single reply list whose contents are swapped before the pull, so the
+    // same route re-serializes fresh data on the refresh request.
+    final items = <Map<String, dynamic>>[
+      notificationJson(id: 1, title: 'Before refresh'),
+    ];
+    adapter.onGet(
+      '/notifications',
+      (server) => server.reply(200, items),
+      queryParameters: {'is_new': true, 'page_offset': 0, 'page_limit': 6},
+    );
+
+    await tester.pumpWidget(
+      MaterialApp(
+        theme: gruvboxDarkTheme,
+        home: const Scaffold(body: NotificationsList()),
+      ),
+    );
+    await tester.pumpAndSettle();
+    expect(find.textContaining('Before refresh'), findsOneWidget);
+
+    // The next fetch returns fresh data; a pull-down should pick it up.
+    items
+      ..clear()
+      ..add(notificationJson(id: 2, title: 'After refresh'));
+    await tester.fling(
+      find.byType(CustomScrollView),
+      const Offset(0, 300),
+      1000,
+    );
+    await tester.pumpAndSettle();
+
+    expect(find.textContaining('After refresh'), findsOneWidget);
+    expect(find.textContaining('Before refresh'), findsNothing);
+
+    await tester.pumpWidget(const SizedBox());
+  });
 }