Move welcome message into first-run backend config dialog

Drop the standalone welcome card from the Settings screen and show the
greeting inside the non-dismissible first-run configuration dialog,
noting that OOTT cannot function without a backend installed in the
network.

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

TODO.md

@@ -31,7 +31,7 @@
 
 ## Frontend
 
-- [ ] Add a note on the settings dialog when empty that you need a backend
+- [x] Add a note on the settings dialog when empty that you need a backend
 - [x] On iOS, the buttons in the Settings configure dialog appear on two lines, try to fit them in one
 - [x] Add more themes (Dracula, Nord, Catppuccin Latte, Gruvbox light)
 - [x] Remove the license and notice from the UI, just link to the github pages

frontend/lib/settings/backend_config_dialog.dart

@@ -163,6 +163,38 @@ class _BackendConfigDialogState extends State<_BackendConfigDialog> {
               mainAxisSize: MainAxisSize.min,
               crossAxisAlignment: CrossAxisAlignment.start,
               children: [
+                // First run: the connection isn't configured yet, so greet the
+                // user and make clear OOTT relies on a backend running in their
+                // network.
+                if (!widget.dismissible) ...[
+                  Card(
+                    color: colorScheme.secondaryContainer,
+                    margin: EdgeInsets.zero,
+                    child: Padding(
+                      padding: const EdgeInsets.all(Insets.lg),
+                      child: Row(
+                        children: [
+                          Icon(
+                            Icons.waving_hand_outlined,
+                            color: colorScheme.onSecondaryContainer,
+                          ),
+                          const SizedBox(width: Insets.md),
+                          Expanded(
+                            child: Text(
+                              'Welcome to OOTT! Point the app at your server’s '
+                              'API to get started. OOTT cannot function without '
+                              'a backend installed in your network.',
+                              style: textTheme.bodyMedium?.copyWith(
+                                color: colorScheme.onSecondaryContainer,
+                              ),
+                            ),
+                          ),
+                        ],
+                      ),
+                    ),
+                  ),
+                  const SizedBox(height: Insets.lg),
+                ],
                 TextFormField(
                   controller: _baseUrlController,
                   onChanged: _onConnectionChanged,

frontend/lib/settings/settings.dart

@@ -170,40 +170,10 @@ class _SettingsState extends State<Settings> {
 
   @override
   Widget build(BuildContext context) {
-    final colorScheme = Theme.of(context).colorScheme;
-    final textTheme = Theme.of(context).textTheme;
-
     return SingleChildScrollView(
       child: Column(
         crossAxisAlignment: CrossAxisAlignment.start,
         children: [
-          if (_isFirstRun) ...[
-            Card(
-              color: colorScheme.secondaryContainer,
-              child: Padding(
-                padding: const EdgeInsets.all(Insets.lg),
-                child: Row(
-                  children: [
-                    Icon(
-                      Icons.waving_hand_outlined,
-                      color: colorScheme.onSecondaryContainer,
-                    ),
-                    const SizedBox(width: Insets.md),
-                    Expanded(
-                      child: Text(
-                        'Welcome to OOTT! Point the app at your server’s API '
-                        'to get started.',
-                        style: textTheme.bodyMedium?.copyWith(
-                          color: colorScheme.onSecondaryContainer,
-                        ),
-                      ),
-                    ),
-                  ],
-                ),
-              ),
-            ),
-            const SizedBox(height: Insets.lg),
-          ],
           _buildConnectionSummary(context),
           const SizedBox(height: Insets.lg),
           _buildAppSettings(context),

frontend/test/widget/settings_test.dart

@@ -88,15 +88,22 @@ void main() {
     );
   });
 
-  testWidgets('shows the welcome intro when no server is configured', (
-    tester,
-  ) async {
-    await PrefUtil.setValue('base_url', '');
-    await pumpScreen(tester, const Settings());
-    await tester.pump(const Duration(milliseconds: 10));
+  testWidgets(
+    'shows the welcome intro in the config dialog when no server is configured',
+    (tester) async {
+      await PrefUtil.setValue('base_url', '');
+      await pumpScreen(tester, const Settings());
+      await tester.pumpAndSettle();
 
-    expect(find.textContaining('Welcome to OOTT'), findsOneWidget);
-  });
+      // The first-run dialog opens automatically and carries the welcome note.
+      expect(find.text('Backend configuration'), findsOneWidget);
+      expect(find.textContaining('Welcome to OOTT'), findsOneWidget);
+      expect(
+        find.textContaining('cannot function without a backend'),
+        findsOneWidget,
+      );
+    },
+  );
 
   testWidgets('hides the welcome intro once a server is configured', (
     tester,