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,
+        );
       },
     );
   }

apps/lib/core/auth/session_store.dart

@@ -14,6 +14,7 @@ class SessionStore {
   static const String _emailKey = 'saved_email';
   static const String _welcomeReadKey = 'has_seen_welcome_dialog';
   static const String _localeKey = 'selected_locale';
+  static const String _timezoneKey = 'selected_timezone';
 
   Future<void> saveToken(String token) async {
     await _secureStorage.write(key: _tokenKey, value: token);
@@ -66,4 +67,12 @@ class SessionStore {
   Future<String?> getLocaleTag() async {
     return _kvStore.getString(_localeKey);
   }
+
+  Future<void> saveTimezone(String timezone) async {
+    await _kvStore.setString(_timezoneKey, timezone);
+  }
+
+  Future<String?> getTimezone() async {
+    return _kvStore.getString(_timezoneKey);
+  }
 }

apps/lib/core/localization/system_locale.dart

@@ -0,0 +1,27 @@
+import 'dart:ui';
+
+Locale? resolveSystemLocale(Locale systemLocale) {
+  final lang = systemLocale.languageCode.toLowerCase();
+  final script = systemLocale.scriptCode;
+  final country = systemLocale.countryCode;
+
+  if (lang == 'en') {
+    return const Locale('en');
+  }
+
+  if (lang == 'zh') {
+    if (script == 'Hant' ||
+        country == 'TW' ||
+        country == 'HK' ||
+        country == 'MO') {
+      return const Locale.fromSubtags(languageCode: 'zh', scriptCode: 'Hant');
+    }
+    return const Locale('zh');
+  }
+
+  return null;
+}
+
+Locale getSystemLocale() {
+  return PlatformDispatcher.instance.locale;
+}

apps/lib/core/timezone/system_timezone.dart

@@ -0,0 +1,5 @@
+import 'package:flutter_timezone/flutter_timezone.dart';
+
+Future<String> getSystemTimezone() async {
+  return FlutterTimezone.getLocalTimezone();
+}

apps/lib/features/auth/data/apis/auth_api.dart

@@ -19,10 +19,18 @@ class AuthApi {
   Future<SessionResponse> createEmailSession({
     required String email,
     required String token,
+    String? language,
+    String? timezone,
   }) async {
+    final data = <String, dynamic>{
+      'email': email,
+      'token': token,
+    };
+    if (language != null) data['language'] = language;
+    if (timezone != null) data['timezone'] = timezone;
     final json = await _apiClient.postJson(
       '/api/v1/auth/email-session',
-      data: {'email': email, 'token': token},
+      data: data,
     );
     return SessionResponse.fromJson(json);
   }

apps/lib/features/auth/data/repositories/auth_repository.dart

@@ -9,6 +9,8 @@ abstract class AuthRepository {
   Future<AuthUser> loginWithEmailOtp({
     required String email,
     required String otp,
+    String? language,
+    String? timezone,
   });
 
   Future<AuthUser?> recoverSession();
@@ -37,8 +39,15 @@ class AuthRepositoryImpl implements AuthRepository {
   Future<AuthUser> loginWithEmailOtp({
     required String email,
     required String otp,
+    String? language,
+    String? timezone,
   }) async {
-    final session = await _authApi.createEmailSession(email: email, token: otp);
+    final session = await _authApi.createEmailSession(
+      email: email,
+      token: otp,
+      language: language,
+      timezone: timezone,
+    );
     await _sessionStore.saveToken(session.accessToken);
     await _sessionStore.saveRefreshToken(session.refreshToken);
     await _sessionStore.saveEmail(email);

apps/lib/features/auth/presentation/bloc/auth_bloc.dart

@@ -50,8 +50,15 @@ class AuthBloc extends ChangeNotifier {
   Future<void> loginWithOtp({
     required String email,
     required String otp,
+    String? language,
+    String? timezone,
   }) async {
-    final user = await _repository.loginWithEmailOtp(email: email, otp: otp);
+    final user = await _repository.loginWithEmailOtp(
+      email: email,
+      otp: otp,
+      language: language,
+      timezone: timezone,
+    );
     _logger.info(message: 'User logged in', extra: {'user_id': user.id});
     _state = AuthState(status: AuthStatus.authenticated, user: user);
     notifyListeners();

apps/lib/shared/utils/time_format.dart

@@ -0,0 +1,30 @@
+import 'package:flutter/widgets.dart';
+
+import '../../l10n/app_localizations.dart';
+
+String formatRelativeTime(BuildContext context, DateTime dateTime) {
+  final l10n = AppLocalizations.of(context)!;
+  final diff = DateTime.now().difference(dateTime);
+  if (diff.inMinutes < 1) return l10n.timeJustNow;
+  if (diff.inHours < 1) return l10n.timeMinutesAgo(diff.inMinutes);
+  if (diff.inDays < 1) return l10n.timeHoursAgo(diff.inHours);
+  if (diff.inDays < 30) return l10n.timeDaysAgo(diff.inDays);
+  return '${dateTime.month}/${dateTime.day}';
+}
+
+String formatCompactLocalDateTime(String isoString) {
+  final dateTime = DateTime.parse(isoString).toLocal();
+  final now = DateTime.now();
+  final timeText =
+      '${dateTime.hour.toString().padLeft(2, '0')}:${dateTime.minute.toString().padLeft(2, '0')}';
+
+  if (now.year == dateTime.year &&
+      now.month == dateTime.month &&
+      now.day == dateTime.day) {
+    return timeText;
+  }
+
+  final dateText =
+      '${dateTime.year}-${dateTime.month.toString().padLeft(2, '0')}-${dateTime.day.toString().padLeft(2, '0')}';
+  return '$dateText $timeText';
+}