feat(feedback): implement user feedback collection system with email reporting

Backend:
- Add user_feedback table with RLS policy
- Create feedback submission API (multipart/form-data)
- Implement xlsx report generation with embedded images
- Add scheduled email delivery via Feishu SMTP
- Create HTML email templates (daily_report, no_feedback)

Frontend:
- Add feedback screen with type selection and image picker
- Support anonymous submission via skipAuth flag
- Collect device info and app version

Protocol:
- Document feedback API contract and error codes
- Update http-error-codes.md with FEEDBACK_* codes

apps/lib/features/home/presentation/screens/home_screen.dart

@@ -73,16 +73,16 @@ class HomeScreen extends StatefulWidget {
 class _HomeScreenState extends State<HomeScreen> {
   MainTab _currentTab = MainTab.home;
   late final InviteRepository _inviteRepository;
+  late final ApiClient _apiClient;
 
   @override
   void initState() {
     super.initState();
-    final inviteApi = InviteApi(
-      apiClient: ApiClient(
-        baseUrl: appDependencies.backendUrl,
-        tokenProvider: widget.sessionStore.getToken,
-      ),
+    _apiClient = ApiClient(
+      baseUrl: appDependencies.backendUrl,
+      tokenProvider: widget.sessionStore.getToken,
     );
+    final inviteApi = InviteApi(apiClient: _apiClient);
     _inviteRepository = InviteRepositoryImpl(inviteApi: inviteApi);
     WidgetsBinding.instance.addPostFrameCallback((_) {
       _tryShowWelcomeDialog();
@@ -135,6 +135,7 @@ class _HomeScreenState extends State<HomeScreen> {
             settings: widget.profileSettings,
             coinBalance: widget.coinBalance,
             inviteRepository: _inviteRepository,
+            apiClient: _apiClient,
             onLocaleChanged: widget.onLocaleChanged,
             onSettingsChanged: widget.onProfileSettingsChanged,
             onSaveProfile: widget.onSaveProfile,
@@ -563,6 +564,7 @@ class _ProfileTab extends StatelessWidget {
     required this.settings,
     required this.coinBalance,
     required this.inviteRepository,
+    required this.apiClient,
     required this.onLocaleChanged,
     required this.onSettingsChanged,
     required this.onSaveProfile,
@@ -575,6 +577,7 @@ class _ProfileTab extends StatelessWidget {
   final ProfileSettingsV1 settings;
   final int coinBalance;
   final InviteRepository inviteRepository;
+  final ApiClient apiClient;
   final Future<void> Function(String languageTag) onLocaleChanged;
   final Future<void> Function(ProfileSettingsV1 settings) onSettingsChanged;
   final Future<ProfileSettingsV1> Function(ProfileSettingsV1 updated)
@@ -590,6 +593,7 @@ class _ProfileTab extends StatelessWidget {
       settings: settings,
       coinBalance: coinBalance,
       inviteRepository: inviteRepository,
+      apiClient: apiClient,
       onInterfaceLanguageChanged: onLocaleChanged,
       onSettingsChanged: onSettingsChanged,
       onSaveProfile: onSaveProfile,