fix(auth): reset countdown after resend and add sending state

apps/lib/features/auth/ui/screens/register_verification_screen.dart

@@ -93,7 +93,12 @@ class _RegisterVerificationViewState extends State<RegisterVerificationView> {
   }
 
   Future<void> _handleResendCode() async {
-    await context.read<RegisterCubit>().resendCode();
+    final cubit = context.read<RegisterCubit>();
+    await cubit.resendCode();
+
+    if (cubit.state.codeSent && mounted) {
+      _startCountdown();
+    }
   }
 
   @override
@@ -235,17 +240,25 @@ class _RegisterVerificationViewState extends State<RegisterVerificationView> {
               ),
             ),
             const SizedBox(width: 8),
-            _buildResendButton(canResend),
+            _buildResendButton(canResend, state),
           ],
         ),
       ],
     );
   }
 
-  Widget _buildResendButton(bool canResend) {
+  Widget _buildResendButton(bool canResend, RegisterState state) {
     final borderColor = canResend ? AppColors.primary : AppColors.slate300;
     final textColor = canResend ? AppColors.primary : AppColors.slate400;
-    final text = canResend ? '重新发送' : '$_countdown s';
+
+    String text;
+    if (state.status == FormzSubmissionStatus.inProgress) {
+      text = '发送中...';
+    } else if (canResend) {
+      text = '重新发送';
+    } else {
+      text = '$_countdown s';
+    }
 
     return SizedBox(
       width: 90,