feat(locale): 实现 App 启动时语言和时区自动设置

- 新增系统语言/时区读取工具函数
- SessionStore 扩展支持时区存储
- 启动流程自动检测并保存系统语言/时区
- 注册时传递语言/时区到后端
- 登录后从服务器同步语言/时区

apps/lib/app/app.dart

@@ -4,7 +4,9 @@ import 'package:flutter/material.dart';
 import 'package:flutter_localizations/flutter_localizations.dart';
 
 import '../core/auth/session_store.dart';
+import '../core/localization/system_locale.dart';
 import '../core/logging/logger.dart';
+import '../core/timezone/system_timezone.dart';
 import '../data/network/api_client.dart';
 import '../data/storage/local_kv_store.dart';
 import '../features/auth/data/apis/auth_api.dart';
@@ -42,6 +44,7 @@ class _EryaoAppState extends State<EryaoApp> {
   late final NotificationRepository _notificationRepository;
   late final NotificationBloc _notificationBloc;
   Locale _locale = const Locale('zh');
+  String _timezone = 'Asia/Shanghai';
   ProfileSettingsV1 _profileSettings = ProfileSettingsV1.defaultsForLocale(
     const Locale('zh'),
   );
@@ -300,11 +303,14 @@ class _EryaoAppState extends State<EryaoApp> {
       if (!mounted) {
         return;
       }
-      final serverLanguage = profile.preferences.interfaceLanguage;
+      final serverLanguage = profile.preferences.language;
+      final serverTimezone = profile.preferences.timezone;
       final serverLocale = localeFromLanguageTag(serverLanguage);
       await _sessionStore.saveLocaleTag(serverLanguage);
+      await _sessionStore.saveTimezone(serverTimezone);
       setState(() {
         _locale = serverLocale;
+        _timezone = serverTimezone;
         _profileSettings = profile;
         _loadedProfileUserEmail = userEmail;
       });
@@ -352,8 +358,8 @@ class _EryaoAppState extends State<EryaoApp> {
 
   Future<void> _saveProfileSettings(ProfileSettingsV1 next) async {
     try {
-      final oldLanguage = _profileSettings.preferences.interfaceLanguage;
-      final newLanguage = next.preferences.interfaceLanguage;
+      final oldLanguage = _profileSettings.preferences.language;
+      final newLanguage = next.preferences.language;
       final saved = await _profileApi.updateSettings(next);
       if (!mounted) {
         return;
@@ -383,13 +389,29 @@ class _EryaoAppState extends State<EryaoApp> {
   }
 
   Future<void> _bootstrap() async {
-    final localeTag = await _sessionStore.getLocaleTag();
-    final locale = localeTag != null
-        ? localeFromLanguageTag(localeTag)
-        : const Locale('zh');
+    final savedLocaleTag = await _sessionStore.getLocaleTag();
+    final Locale locale;
+    if (savedLocaleTag != null) {
+      locale = localeFromLanguageTag(savedLocaleTag);
+    } else {
+      final systemLocale = getSystemLocale();
+      locale = resolveSystemLocale(systemLocale) ?? const Locale('zh');
+      await _sessionStore.saveLocaleTag(languageTagFromLocale(locale));
+    }
+
+    final savedTimezone = await _sessionStore.getTimezone();
+    final String timezone;
+    if (savedTimezone != null) {
+      timezone = savedTimezone;
+    } else {
+      timezone = await getSystemTimezone();
+      await _sessionStore.saveTimezone(timezone);
+    }
+
     if (mounted) {
       setState(() {
         _locale = locale;
+        _timezone = timezone;
         _profileSettings = ProfileSettingsV1.defaultsForLocale(locale);
       });
     }
@@ -406,7 +428,7 @@ class _EryaoAppState extends State<EryaoApp> {
       _locale = locale;
       _profileSettings = _profileSettings.copyWith(
         preferences: _profileSettings.preferences.copyWith(
-          interfaceLanguage: languageTag,
+          language: languageTag,
         ),
       );
     });
@@ -486,7 +508,12 @@ class _EryaoAppState extends State<EryaoApp> {
       onLocaleChanged: (_) {},
       onRequestOtp: _authBloc.sendOtp,
       onLoginWithOtp: (email, otp) {
-        return _authBloc.loginWithOtp(email: email, otp: otp);
+        return _authBloc.loginWithOtp(
+          email: email,
+          otp: otp,
+          language: languageTagFromLocale(_locale),
+          timezone: _timezone,
+        );
       },
     );
   }