feat(auth): add sendCodeSilently with isSending state

apps/lib/features/auth/presentation/cubits/register_cubit.dart

@@ -16,6 +16,7 @@ class RegisterState extends Equatable {
   final String? errorMessage;
   final String? pendingEmail;
   final bool codeSent;
+  final bool isSending;
 
   const RegisterState({
     this.username = const Username.pure(),
@@ -26,6 +27,7 @@ class RegisterState extends Equatable {
     this.errorMessage,
     this.pendingEmail,
     this.codeSent = false,
+    this.isSending = false,
   });
 
   bool get isStep1Valid =>
@@ -41,6 +43,7 @@ class RegisterState extends Equatable {
     String? errorMessage,
     String? pendingEmail,
     bool? codeSent,
+    bool? isSending,
   }) {
     return RegisterState(
       username: username ?? this.username,
@@ -51,6 +54,7 @@ class RegisterState extends Equatable {
       errorMessage: errorMessage,
       pendingEmail: pendingEmail ?? this.pendingEmail,
       codeSent: codeSent ?? this.codeSent,
+      isSending: isSending ?? this.isSending,
     );
   }
 
@@ -64,6 +68,7 @@ class RegisterState extends Equatable {
     errorMessage,
     pendingEmail,
     codeSent,
+    isSending,
   ];
 }
 
@@ -160,4 +165,31 @@ class RegisterCubit extends Cubit<RegisterState> {
       emit(state.copyWith(errorMessage: message));
     }
   }
+
+  Future<void> sendCodeSilently() async {
+    if (!state.isStep1Valid) return;
+
+    emit(state.copyWith(isSending: true));
+
+    try {
+      final response = await _repository.signupStart(
+        SignupStartRequest(
+          username: state.username.value,
+          email: state.email.value,
+          password: state.password.value,
+        ),
+      );
+      emit(
+        state.copyWith(
+          isSending: false,
+          pendingEmail: response.email,
+          codeSent: true,
+          errorMessage: null,
+        ),
+      );
+    } catch (e) {
+      final message = e is ApiException ? e.message : '验证码发送失败，请重试';
+      emit(state.copyWith(isSending: false, errorMessage: message));
+    }
+  }
 }

apps/test/features/auth/presentation/cubits/register_cubit_test.dart

@@ -2,7 +2,10 @@ import 'package:bloc_test/bloc_test.dart';
 import 'package:flutter_test/flutter_test.dart';
 import 'package:formz/formz.dart';
 import 'package:mocktail/mocktail.dart';
+import 'package:social_app/core/form_inputs/form_inputs.dart';
 import 'package:social_app/features/auth/data/auth_repository.dart';
+import 'package:social_app/features/auth/data/models/auth_response.dart';
+import 'package:social_app/features/auth/data/models/signup_request.dart';
 import 'package:social_app/features/auth/presentation/cubits/register_cubit.dart';
 
 class MockAuthRepository extends Mock implements AuthRepository {}
@@ -14,6 +17,9 @@ void main() {
   setUp(() {
     mockRepository = MockAuthRepository();
     cubit = RegisterCubit(mockRepository);
+    registerFallbackValue(
+      SignupStartRequest(username: '', email: '', password: ''),
+    );
   });
 
   tearDown(() {
@@ -46,4 +52,39 @@ void main() {
       expect: () => [isA<RegisterState>()],
     );
   });
+
+  group('sendCodeSilently', () {
+    blocTest<RegisterCubit, RegisterState>(
+      'sets isSending to true then false on success',
+      build: () => cubit,
+      seed: () => RegisterState(
+        username: const Username.dirty('testuser'),
+        email: const Email.dirty('test@example.com'),
+        password: const Password.dirty('password123'),
+      ),
+      setUp: () {
+        when(() => mockRepository.signupStart(any())).thenAnswer(
+          (_) async => SignupStartResponse(
+            status: 'ok',
+            email: 'test@example.com',
+            message: 'Code sent',
+          ),
+        );
+      },
+      act: (c) => c.sendCodeSilently(),
+      expect: () => [
+        predicate<RegisterState>((state) => state.isSending == true),
+        predicate<RegisterState>(
+          (state) =>
+              state.isSending == false &&
+              state.codeSent == true &&
+              state.pendingEmail == 'test@example.com' &&
+              state.errorMessage == null,
+        ),
+      ],
+      verify: (_) {
+        verify(() => mockRepository.signupStart(any())).called(1);
+      },
+    );
+  });
 }