💄 style(wechat): adjust wechat callback page layout

- change container class from "text-center" to "flex flex-col items-center" for better layout control

src/client/mobile/pages/WechatCallbackPage.tsx

@@ -90,7 +90,7 @@ const WechatCallbackPage: React.FC = () => {
 
   return (
     <div className="flex justify-center items-center min-h-screen bg-gray-100">
-      <div className="text-center">
+      <div className="flex flex-col items-center">
         {getStatusIcon()}
         <h2 className="mt-4 text-lg font-medium text-gray-900">
           {status === 'loading' && '微信登录处理中...'}