feat: 登陆注册UI调整，用户协议和隐私政策跳转调整

src/components/PrivacyPolicyModal.js

@@ -18,6 +18,11 @@ const PrivacyPolicyModal = ({ isOpen, onClose }) => {
   const headingColor = useColorModeValue("gray.800", "white");
   const textColor = useColorModeValue("gray.600", "gray.300");
 
+  // Conditional rendering: only render Modal when open
+  if (!isOpen) {
+    return null;
+  }
+
   return (
     <Modal 
       isOpen={isOpen}