feat: enforce hierarchical back navigation and home-only exit

apps/lib/core/router/app_router.dart

@@ -26,15 +26,19 @@ import '../../features/settings/ui/screens/features_screen.dart';
 import '../../features/settings/ui/screens/memory_screen.dart';
 import '../../features/settings/ui/screens/edit_profile_screen.dart';
 
-final _protectedRoutes = [
+final _homeSecondLevelRoutes = [
   AppRoutes.homeMain,
-  AppRoutes.contactsList,
-  AppRoutes.contactsAdd,
   AppRoutes.calendarDayWeek,
   AppRoutes.calendarMonth,
-  '/calendar/events',
   AppRoutes.todoList,
   AppRoutes.settingsMain,
+];
+
+final _protectedRoutes = [
+  ..._homeSecondLevelRoutes,
+  AppRoutes.contactsList,
+  AppRoutes.contactsAdd,
+  '/calendar/events',
   AppRoutes.settingsFeatures,
   AppRoutes.settingsMemory,
   AppRoutes.settingsEditProfile,

apps/lib/features/calendar/ui/screens/calendar_dayweek_screen.dart

@@ -119,7 +119,7 @@ class _CalendarDayWeekScreenState extends State<CalendarDayWeekScreen>
         canPop: false,
         onPopInvokedWithResult: (didPop, result) {
           if (!didPop) {
-            returnToHomePreserveState(context);
+            returnToHomePreserveState(context, forceGoHome: true);
           }
         },
         child: SafeArea(
@@ -702,7 +702,7 @@ class _CalendarDayWeekScreenState extends State<CalendarDayWeekScreen>
         _calendarManager.setViewType(CalendarViewType.day);
         context.push(AppRoutes.calendarMonth);
       },
-      onHomeTap: () => returnToHomePreserveState(context),
+      onHomeTap: () => returnToHomePreserveState(context, forceGoHome: true),
     );
   }
 }

apps/lib/features/calendar/ui/screens/calendar_month_screen.dart

@@ -105,7 +105,7 @@ class _CalendarMonthScreenState extends State<CalendarMonthScreen>
         canPop: false,
         onPopInvokedWithResult: (didPop, result) {
           if (!didPop) {
-            returnToHomePreserveState(context);
+            returnToHomePreserveState(context, forceGoHome: true);
           }
         },
         child: SafeArea(
@@ -522,7 +522,7 @@ class _CalendarMonthScreenState extends State<CalendarMonthScreen>
         context.push(AppRoutes.todoList);
       },
       onCalendarTap: () {},
-      onHomeTap: () => returnToHomePreserveState(context),
+      onHomeTap: () => returnToHomePreserveState(context, forceGoHome: true),
     );
   }
 }

apps/lib/features/home/ui/navigation/home_return_policy.dart

@@ -8,7 +8,11 @@ enum HomeReturnAction { pop, goHome }
 HomeReturnAction resolveHomeReturnAction({
   required bool canPop,
   required bool isAuthEntry,
+  bool forceGoHome = false,
 }) {
+  if (forceGoHome) {
+    return HomeReturnAction.goHome;
+  }
   if (isAuthEntry) {
     return HomeReturnAction.goHome;
   }
@@ -21,10 +25,12 @@ HomeReturnAction resolveHomeReturnAction({
 void returnToHomePreserveState(
   BuildContext context, {
   bool isAuthEntry = false,
+  bool forceGoHome = false,
 }) {
   final action = resolveHomeReturnAction(
     canPop: context.canPop(),
     isAuthEntry: isAuthEntry,
+    forceGoHome: forceGoHome,
   );
   switch (action) {
     case HomeReturnAction.pop:

apps/lib/features/settings/ui/screens/settings_screen.dart

@@ -20,6 +20,7 @@ import 'package:social_app/features/settings/data/settings_api.dart';
 import 'package:social_app/features/settings/data/services/settings_user_cache.dart';
 import 'package:social_app/features/users/data/models/user_response.dart';
 import 'package:social_app/features/users/data/users_api.dart';
+import 'package:social_app/features/home/ui/navigation/home_return_policy.dart';
 import '../widgets/settings_page_scaffold.dart';
 
 const settingsProfileEditButtonKey = ValueKey('settings_profile_edit_button');
@@ -90,7 +91,7 @@ class _SettingsScreenState extends State<SettingsScreen> {
   Widget build(BuildContext context) {
     return SettingsPageScaffold(
       title: '设置',
-      onBack: () => context.pop(),
+      onBack: () => returnToHomePreserveState(context, forceGoHome: true),
       body: Column(
         crossAxisAlignment: CrossAxisAlignment.stretch,
         children: [

apps/lib/features/todo/ui/screens/todo_quadrants_screen.dart

@@ -298,7 +298,7 @@ class _TodoQuadrantsScreenState extends State<TodoQuadrantsScreen> {
         canPop: false,
         onPopInvokedWithResult: (didPop, result) {
           if (!didPop) {
-            returnToHomePreserveState(context);
+            returnToHomePreserveState(context, forceGoHome: true);
           }
         },
         child: SafeArea(
@@ -563,7 +563,7 @@ class _TodoQuadrantsScreenState extends State<TodoQuadrantsScreen> {
           context.push('${AppRoutes.calendarDayWeek}?date=$dateStr');
         }
       },
-      onHomeTap: () => returnToHomePreserveState(context),
+      onHomeTap: () => returnToHomePreserveState(context, forceGoHome: true),
     );
   }
 }

apps/test/features/home/ui/navigation/home_return_policy_test.dart

@@ -3,6 +3,15 @@ import 'package:social_app/features/home/ui/navigation/home_return_policy.dart';
 
 void main() {
   group('resolveHomeReturnAction', () {
+    test('second-level pages should return to home instead of exiting app', () {
+      final action = resolveHomeReturnAction(
+        canPop: false,
+        isAuthEntry: false,
+        forceGoHome: true,
+      );
+      expect(action, HomeReturnAction.goHome);
+    });
+
     test('business route with back stack prefers pop', () {
       final action = resolveHomeReturnAction(canPop: true, isAuthEntry: false);
       expect(action, HomeReturnAction.pop);