Add mode switching and fix logout flow in settings

- Display current app mode in settings
- Add dialog to switch between local and online modes
- Fix logout to reset setup state and return to setup screen

lib/features/settings/presentation/pages/settings_page.dart

@@ -4,6 +4,7 @@ import 'package:go_router/go_router.dart';
 import 'package:provider/provider.dart';
 
 import '../../../auth/presentation/viewmodels/auth_viewmodel.dart';
+import '../../domain/enums/app_mode.dart';
 import '../viewmodels/settings_viewmodel.dart';
 
 class SettingsPage extends StatelessWidget {
@@ -24,6 +25,21 @@ class SettingsPage extends StatelessWidget {
       ),
       body: ListView(
         children: [
+          _SectionHeader(title: l10n.appMode),
+          ListTile(
+            leading: Icon(
+              settingsVm.isLocalMode ? Icons.smartphone : Icons.cloud_sync,
+            ),
+            title: Text(settingsVm.isLocalMode ? l10n.localMode : l10n.onlineMode),
+            subtitle: Text(
+              settingsVm.isLocalMode
+                  ? l10n.useLocallyDesc
+                  : l10n.syncOnlineDesc,
+            ),
+            trailing: const Icon(Icons.chevron_right),
+            onTap: () => _showModeSwitchDialog(context, settingsVm, l10n),
+          ),
+          const Divider(),
           _SectionHeader(title: l10n.general),
           ListTile(
             leading: const Icon(Icons.language),
@@ -48,6 +64,8 @@ class SettingsPage extends StatelessWidget {
             title: Text(l10n.version),
             subtitle: const Text('1.0.0'),
           ),
+          // Only show logout button in online mode when authenticated
+          if (settingsVm.isOnlineMode) ...[
             const Divider(),
             const SizedBox(height: 16),
             Padding(
@@ -65,6 +83,7 @@ class SettingsPage extends StatelessWidget {
                 ),
               ),
             ),
+          ],
           const SizedBox(height: 32),
         ],
       ),
@@ -110,6 +129,79 @@ class SettingsPage extends StatelessWidget {
     );
   }
 
+  void _showModeSwitchDialog(
+    BuildContext context,
+    SettingsViewModel settingsVm,
+    AppLocalizations l10n,
+  ) {
+    final isLocalMode = settingsVm.isLocalMode;
+
+    showDialog(
+      context: context,
+      builder: (dialogContext) => AlertDialog(
+        title: Text(isLocalMode ? l10n.switchToOnline : l10n.switchToLocal),
+        content: Text(l10n.switchModeWarning),
+        actions: [
+          TextButton(
+            onPressed: () => Navigator.pop(dialogContext),
+            child: Text(l10n.cancel),
+          ),
+          FilledButton(
+            onPressed: () async {
+              Navigator.pop(dialogContext);
+
+              if (isLocalMode) {
+                // Switching from local to online
+                // First, ask if user wants to upload local tasks
+                final uploadTasks = await _showUploadTasksDialog(context, l10n);
+
+                if (uploadTasks == true) {
+                  // TODO: Implement task upload to server after login
+                  // For now, just switch mode and go to login
+                }
+
+                await settingsVm.setAppMode(AppMode.online);
+                if (context.mounted) {
+                  context.go('/login');
+                }
+              } else {
+                // Switching from online to local
+                await context.read<AuthViewModel>().logout();
+                await settingsVm.setAppMode(AppMode.local);
+                if (context.mounted) {
+                  context.go('/');
+                }
+              }
+            },
+            child: Text(isLocalMode ? l10n.switchToOnline : l10n.switchToLocal),
+          ),
+        ],
+      ),
+    );
+  }
+
+  Future<bool?> _showUploadTasksDialog(
+    BuildContext context,
+    AppLocalizations l10n,
+  ) async {
+    return showDialog<bool>(
+      context: context,
+      builder: (dialogContext) => AlertDialog(
+        title: Text(l10n.uploadTasksQuestion),
+        actions: [
+          TextButton(
+            onPressed: () => Navigator.pop(dialogContext, false),
+            child: Text(l10n.no),
+          ),
+          FilledButton(
+            onPressed: () => Navigator.pop(dialogContext, true),
+            child: Text(l10n.yes),
+          ),
+        ],
+      ),
+    );
+  }
+
   void _showLogoutConfirmation(BuildContext context, AppLocalizations l10n) {
     showDialog(
       context: context,
@@ -122,9 +214,17 @@ class SettingsPage extends StatelessWidget {
             child: Text(l10n.cancel),
           ),
           FilledButton(
-            onPressed: () {
+            onPressed: () async {
+              final authVm = context.read<AuthViewModel>();
+              final settingsVm = context.read<SettingsViewModel>();
               Navigator.pop(dialogContext);
-              context.read<AuthViewModel>().logout();
+              await authVm.logout();
+              // Reset setup so user returns to setup screen on next launch
+              await settingsVm.setSetupCompleted(false);
+              await settingsVm.setOnboardingShown(false);
+              if (context.mounted) {
+                context.go('/setup');
+              }
             },
             style: FilledButton.styleFrom(
               backgroundColor: Theme.of(context).colorScheme.error,