fix: 5 critical payment issues from code review

1. Move notify route before authMiddleware (WeChat callback has no JWT)
2. Add await to verifyNotifySignature call (was fire-and-forget)
3. Remove dangerous verify fallback — all signature failures now throw
4. Payment sync polls 3x before giving up, never redirects to success
   page unless confirmed paid
5. Production guard enforces all WX_MCH_* env vars on startup

miniprogram/pages/subscribe-plans/subscribe-plans.js

@@ -200,27 +200,34 @@ Page({
 
   syncAndRedirect: function (orderId, planKey) {
     var self = this
-    api.syncPaymentOrder(orderId).then(function (result) {
-      self.setData({ purchasing: false })
-      if (result.status === 'paid') {
-        wx.showToast({ title: '支付成功', icon: 'success' })
-        setTimeout(function () {
-          wx.redirectTo({ url: '/pages/subscribe-success/subscribe-success?plan=' + planKey })
-        }, 1000)
-      } else {
-        // Callback may not have arrived yet, still redirect optimistically
-        wx.showToast({ title: '支付处理中', icon: 'none' })
-        setTimeout(function () {
-          wx.redirectTo({ url: '/pages/subscribe-success/subscribe-success?plan=' + planKey })
-        }, 2000)
-      }
-    }).catch(function () {
-      self.setData({ purchasing: false })
-      // Even if sync fails, payment may still succeed via callback
-      wx.showToast({ title: '支付处理中，请稍后查看', icon: 'none' })
-      setTimeout(function () {
-        wx.redirectTo({ url: '/pages/subscribe-success/subscribe-success?plan=' + planKey })
-      }, 2000)
-    })
+    var retryCount = 0
+    var maxRetries = 3
+
+    function pollSync() {
+      api.syncPaymentOrder(orderId).then(function (result) {
+        if (result.status === 'paid') {
+          self.setData({ purchasing: false })
+          wx.showToast({ title: '支付成功', icon: 'success' })
+          setTimeout(function () {
+            wx.redirectTo({ url: '/pages/subscribe-success/subscribe-success?plan=' + planKey })
+          }, 1000)
+        } else if (retryCount < maxRetries) {
+          retryCount++
+          setTimeout(pollSync, 2000)
+        } else {
+          self.setData({ purchasing: false })
+          wx.showToast({ title: '支付处理中，请稍后在订阅页查看', icon: 'none' })
+        }
+      }).catch(function () {
+        if (retryCount < maxRetries) {
+          retryCount++
+          setTimeout(pollSync, 2000)
+        } else {
+          self.setData({ purchasing: false })
+          wx.showToast({ title: '支付处理中，请稍后在订阅页查看', icon: 'none' })
+        }
+      })
+    }
+    pollSync()
   }
 })