fix: skip OAuth2 JSAPI flow, use Native QR code directly for WeChat browser

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

web/product-intro/gut-testing.html

@@ -367,31 +367,8 @@ function submitOrder() {
   // 保存联系人信息到全局变量，供后续函数使用
   window._orderContact = { name: name, phone: phone, address: address };
   
-  // 获取openid后进行JSAPI支付
-  var openid = getUrlParam('openid');
-  if (openid) {
-    // 已有openid，直接JSAPI支付
-    doJsapiPay(orderNo, openid);
-  } else if (isWechatBrowser()) {
-    // 微信浏览器内，先跳转OAuth2获取openid
-    fetch('/api/payment/wechat/oauth2-url', {
-      method: 'POST',
-      headers: { 'Content-Type': 'application/json' },
-      body: JSON.stringify({ redirectUri: window.location.href.split('?')[0] + '?orderNo=' + orderNo })
-    })
-    .then(function(r) { return r.json(); })
-    .then(function(data) {
-      if (data.code === 200 && data.data.url) {
-        window.location.href = data.data.url;
-      } else {
-        fallbackNativePay(orderNo);
-      }
-    })
-    .catch(function() { fallbackNativePay(orderNo); });
-  } else {
-    // 非微信浏览器，走Native扫码
-    fallbackNativePay(orderNo);
-  }
+  // 直接走Native扫码支付（微信浏览器内也走扫码，避免OAuth2权限问题）
+  fallbackNativePay(orderNo);
 }
 
 function doJsapiPay(orderNo, openid) {