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/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);