Fix empty-state layout: compact message instead of viewport-filling indicator

Replace Center-in-Expanded / SliverFillRemaining empty states in the
notifications and devices lists with compact, centered inline text so
status widgets below remain visible without scrolling. Also align
notification filter chips to match the devices list spacing.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/lib/devices/device_list.dart

@@ -156,26 +156,37 @@ class _DeviceListState extends State<DeviceList> {
                 .toList(),
           ),
         ),
-        Expanded(
-          child: _isLoading
-              ? const Center(child: CircularProgressIndicator())
-              : _error != null
-              ? Center(child: Text('Error: $_error'))
-              : _devices.isEmpty
-              ? Center(child: Text(_emptyMessage()))
-              : RefreshIndicator(
-                  onRefresh: _loadDevices,
-                  child: ListView.builder(
-                    physics: const AlwaysScrollableScrollPhysics(),
-                    itemCount: _devices.length,
-                    itemBuilder: (context, index) => _DeviceCard(
-                      device: _devices[index],
-                      formatter: formatter,
-                      onRefresh: _loadDevices,
-                    ),
-                  ),
+        if (_isLoading)
+          const Expanded(child: Center(child: CircularProgressIndicator()))
+        else if (_error != null)
+          Expanded(child: Center(child: Text('Error: $_error')))
+        else if (_devices.isEmpty)
+          Padding(
+            padding: const EdgeInsets.only(top: 16, bottom: 12),
+            child: Center(
+              child: Text(
+                _emptyMessage(),
+                style: Theme.of(context).textTheme.bodyMedium?.copyWith(
+                  color: Theme.of(context).colorScheme.onSurfaceVariant,
                 ),
-        ),
+              ),
+            ),
+          )
+        else
+          Expanded(
+            child: RefreshIndicator(
+              onRefresh: _loadDevices,
+              child: ListView.builder(
+                physics: const AlwaysScrollableScrollPhysics(),
+                itemCount: _devices.length,
+                itemBuilder: (context, index) => _DeviceCard(
+                  device: _devices[index],
+                  formatter: formatter,
+                  onRefresh: _loadDevices,
+                ),
+              ),
+            ),
+          ),
       ],
     );
   }

frontend/lib/home/home_screen.dart

@@ -167,10 +167,27 @@ class _HomeScreenState extends State<HomeScreen> {
     PagingState<int, oott_model.Notification> state,
     void Function() fetchNextPage,
   ) {
+    final isEmpty =
+        !state.isLoading && state.items != null && state.items!.isEmpty;
     return CustomScrollView(
       slivers: [
         SliverToBoxAdapter(child: _buildNotificationsHeader(context, state)),
-        _buildNotificationSliver(state, fetchNextPage),
+        if (isEmpty)
+          SliverToBoxAdapter(
+            child: Padding(
+              padding: const EdgeInsets.only(top: 16, bottom: 12),
+              child: Center(
+                child: Text(
+                  'No items found',
+                  style: Theme.of(context).textTheme.bodyMedium?.copyWith(
+                    color: Theme.of(context).colorScheme.onSurfaceVariant,
+                  ),
+                ),
+              ),
+            ),
+          )
+        else
+          _buildNotificationSliver(state, fetchNextPage),
         const SliverToBoxAdapter(
           child: Padding(
             padding: EdgeInsets.only(top: 24),
@@ -212,6 +229,7 @@ class _HomeScreenState extends State<HomeScreen> {
         ),
         SingleChildScrollView(
           scrollDirection: Axis.horizontal,
+          padding: const EdgeInsets.symmetric(horizontal: 8, vertical: 6),
           child: Wrap(
             spacing: 8.0,
             children: _NotificationFilter.values
@@ -228,7 +246,6 @@ class _HomeScreenState extends State<HomeScreen> {
                 .toList(),
           ),
         ),
-        const SizedBox(height: 8),
       ],
     );
   }