feat(auth): add sendCodeSilently with isSending state

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);
+      },
+    );
+  });
 }