fix(android): intercept back during cold startup and move exit toast down

ui/flutter/test/app/router/app_startup_back_test.dart

@@ -0,0 +1,65 @@
+import 'dart:async';
+
+import 'package:flutter/services.dart';
+import 'package:flutter/widgets.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:gopeed/app/application/app_runtime_controller.dart';
+import 'package:gopeed/app/router/app_router.dart';
+import 'package:gopeed/features/auth/application/web_auth_controller.dart';
+import 'package:gopeed/shared/theme/app_theme.dart';
+import 'package:gopeed/shared/widgets/app_toast.dart';
+import 'package:shadcn_flutter/shadcn_flutter.dart' as shad;
+
+class _StartingRuntime extends AppRuntimeController {
+  final pending = Completer<AppRuntimeState>();
+
+  @override
+  Future<AppRuntimeState> build() => pending.future;
+}
+
+void main() {
+  testWidgets(
+    'cold startup registers Android back and confirms exit before runtime is ready',
+    (tester) async {
+      final platformCalls = <MethodCall>[];
+      tester.binding.defaultBinaryMessenger.setMockMethodCallHandler(SystemChannels.platform, (call) async {
+        platformCalls.add(call);
+        return null;
+      });
+      addTearDown(() => tester.binding.defaultBinaryMessenger.setMockMethodCallHandler(SystemChannels.platform, null));
+      final runtime = _StartingRuntime();
+      final auth = WebAuthController();
+      final router = AppRouter.build(auth);
+      addTearDown(router.dispose);
+      addTearDown(auth.dispose);
+      tester.binding.handleAppLifecycleStateChanged(AppLifecycleState.resumed);
+      await tester.pumpWidget(
+        ProviderScope(
+          overrides: [appRuntimeControllerProvider.overrideWith(() => runtime)],
+          child: shad.ShadcnApp.router(
+            theme: AppTheme.dark(),
+            materialTheme: AppTheme.materialDark(),
+            routerConfig: router,
+          ),
+        ),
+      );
+      await tester.pump();
+      await tester.pump();
+      expect(find.byType(shad.CircularProgressIndicator), findsOneWidget);
+      expect(
+        platformCalls.where((call) => call.method == 'SystemNavigator.setFrameworkHandlesBack').last.arguments,
+        isTrue,
+      );
+      await tester.binding.handlePopRoute();
+      await tester.pump();
+      expect(platformCalls.where((call) => call.method == 'SystemNavigator.pop'), isEmpty);
+      expect(find.byType(AppToastContent), findsOneWidget);
+      await tester.binding.handlePopRoute();
+      await tester.pump();
+      expect(platformCalls.where((call) => call.method == 'SystemNavigator.pop'), hasLength(1));
+      await tester.pumpWidget(const SizedBox());
+    },
+    variant: TargetPlatformVariant.only(TargetPlatform.android),
+  );
+}

ui/flutter/test/app/router/mobile_exit_guard_test.dart

@@ -24,11 +24,11 @@ void main() {
     router = GoRouter(
       routes: [
         ShellRoute(
-          builder: (_, _, child) => child,
+          builder: (_, _, child) => MobileExitGuard(child: child),
           routes: [
             GoRoute(
               path: '/',
-              builder: (_, _) => const MobileExitGuard(child: SizedBox.expand()),
+              builder: (_, _) => const SizedBox.expand(),
               routes: [
                 GoRoute(path: 'details', builder: (_, _) => const SizedBox.expand()),
                 for (final path in ['extensions', 'settings'])
@@ -56,13 +56,14 @@ void main() {
     await tester.pumpAndSettle();
   }
 
-  testWidgets('root back shows centered prompt, second back exits', (tester) async {
+  testWidgets('root back shows bottom prompt, second back exits', (tester) async {
     await mount(tester);
     await tester.binding.handlePopRoute();
     await tester.pump();
     expect(exits, isEmpty);
     expect(find.byType(AppToastContent), findsOneWidget);
-    expect(tester.getCenter(find.byType(AppToastContent)), const Offset(400, 300));
+    expect(tester.getCenter(find.byType(AppToastContent)).dx, 400);
+    expect(tester.getBottomLeft(find.byType(AppToastContent)).dy, 576);
     await tester.pump(const Duration(milliseconds: 1900));
     await tester.binding.handlePopRoute();
     await tester.pump();
@@ -127,4 +128,34 @@ void main() {
       expect(exits, hasLength(1));
     }, variant: TargetPlatformVariant.only(TargetPlatform.android));
   }
+  testWidgets(
+    'dialog back dismisses the dialog before exit confirmation',
+    (tester) async {
+      await mount(tester);
+      final context = router.routerDelegate.navigatorKey.currentContext!;
+      showGeneralDialog<void>(
+        context: context,
+        pageBuilder: (_, _, _) => const Center(child: Text('Dialog content')),
+      );
+      await tester.pumpAndSettle();
+      await tester.binding.handlePopRoute();
+      await tester.pumpAndSettle();
+      expect(find.text('Dialog content'), findsNothing);
+      expect(find.byType(AppToastContent), findsNothing);
+      expect(exits, isEmpty);
+    },
+    variant: TargetPlatformVariant.only(TargetPlatform.android),
+  );
+
+  testWidgets('bottom prompt stays above the Android safe area', (tester) async {
+    tester.view.padding = const FakeViewPadding(bottom: 48);
+    tester.view.devicePixelRatio = 1;
+    addTearDown(tester.view.resetPadding);
+    addTearDown(tester.view.resetDevicePixelRatio);
+    await mount(tester);
+    await tester.binding.handlePopRoute();
+    await tester.pump();
+    expect(tester.getBottomLeft(find.byType(AppToastContent)).dy, tester.view.physicalSize.height - 48 - 24);
+    await tester.pumpWidget(const SizedBox());
+  }, variant: TargetPlatformVariant.only(TargetPlatform.android));
 }