feat(auth): improve resend button style with countdown

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

@@ -201,6 +201,9 @@ class _RegisterVerificationViewState extends State<RegisterVerificationView> {
   }
 
   Widget _buildCodeInput(RegisterState state) {
+    final canResend =
+        _countdown == 0 && state.status != FormzSubmissionStatus.inProgress;
+
     return Column(
       crossAxisAlignment: CrossAxisAlignment.start,
       children: [
@@ -232,36 +235,40 @@ class _RegisterVerificationViewState extends State<RegisterVerificationView> {
               ),
             ),
             const SizedBox(width: 8),
-            SizedBox(
-              width: 112,
-              height: 40,
-              child: OutlinedButton(
-                onPressed: state.status == FormzSubmissionStatus.inProgress
-                    ? null
-                    : _handleResendCode,
-                style: OutlinedButton.styleFrom(
-                  backgroundColor: AppColors.background,
-                  side: const BorderSide(color: AppColors.input),
-                  shape: RoundedRectangleBorder(
-                    borderRadius: BorderRadius.circular(6),
-                  ),
-                ),
-                child: const Text(
-                  '发送验证码',
-                  style: TextStyle(
-                    fontSize: 13,
-                    fontWeight: FontWeight.w500,
-                    color: AppColors.slate500,
-                  ),
-                ),
-              ),
-            ),
+            _buildResendButton(canResend),
           ],
         ),
       ],
     );
   }
 
+  Widget _buildResendButton(bool canResend) {
+    final borderColor = canResend ? AppColors.primary : AppColors.slate300;
+    final textColor = canResend ? AppColors.primary : AppColors.slate400;
+    final text = canResend ? '重新发送' : '$_countdown s';
+
+    return SizedBox(
+      width: 90,
+      height: 40,
+      child: OutlinedButton(
+        onPressed: canResend ? _handleResendCode : null,
+        style: OutlinedButton.styleFrom(
+          backgroundColor: AppColors.background,
+          side: BorderSide(color: borderColor),
+          shape: RoundedRectangleBorder(borderRadius: BorderRadius.circular(8)),
+        ),
+        child: Text(
+          text,
+          style: TextStyle(
+            fontSize: 13,
+            fontWeight: FontWeight.w500,
+            color: textColor,
+          ),
+        ),
+      ),
+    );
+  }
+
   Widget _buildStepIndicator() {
     return Row(
       children: [