fix(auth): validation toast and rate limit adjustment

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

@@ -82,6 +82,15 @@ class _RegisterVerificationViewState extends State<RegisterVerificationView> {
     cubit.verificationCodeChanged(_codeController.text);
 
     if (!cubit.state.isStep2Valid) {
+      String? errorMsg;
+      if (_codeController.text.isEmpty) {
+        errorMsg = '请输入验证码';
+      } else {
+        errorMsg = '验证码必须是 6 位数字';
+      }
+      if (mounted) {
+        Toast.show(context, errorMsg, type: ToastType.warning);
+      }
       return;
     }
 
@@ -260,8 +269,8 @@ class _RegisterVerificationViewState extends State<RegisterVerificationView> {
   }
 
   Widget _buildResendButton(bool canResend, RegisterState state) {
-    final borderColor = canResend ? AppColors.primary : AppColors.slate300;
-    final textColor = canResend ? AppColors.primary : AppColors.slate400;
+    final bgColor = canResend ? AppColors.primary : const Color(0xFFF1F5F9);
+    final textColor = canResend ? AppColors.white : AppColors.slate400;
 
     String text;
     if (state.status == FormzSubmissionStatus.inProgress) {
@@ -278,7 +287,7 @@ class _RegisterVerificationViewState extends State<RegisterVerificationView> {
         width: 70,
         height: 40,
         decoration: BoxDecoration(
-          border: Border.all(color: borderColor),
+          color: bgColor,
           borderRadius: BorderRadius.circular(6),
         ),
         alignment: Alignment.center,

backend/src/v1/auth/router.py

@@ -63,7 +63,7 @@ async def signup_resend(
     await enforce_rate_limit(
         scope="signup_resend",
         identifier=payload.email,
-        limit=3,
+        limit=5,
         window_seconds=60,
     )
     return await service.signup_resend(payload)