feat: 支付成功页与友好 webhook 落地页

浏览器回跳展示许可证并深链回 App；补齐包年订单因未收到 Waffo POST 未发码的体验。

Co-authored-by: Cursor <cursoragent@cursor.com>

backend/router/router.go

@@ -111,6 +111,7 @@ func SetupRouter(db *gorm.DB, cfg *config.Config) *gin.Engine {
 			register(clientAPI, "POST", "/webhooks/payment", orderController.PaymentWebhook)
 			register(clientAPI, "GET", "/webhooks/waffo", orderController.WaffoWebhookReady)
 			register(clientAPI, "POST", "/webhooks/waffo", orderController.WaffoWebhook)
+			register(clientAPI, "GET", "/purchase/success", orderController.PurchaseSuccess)
 			register(clientAPI, "POST", "/purchase/check", orderController.CheckDuplicatePurchase)
 			register(clientAPI, "POST", "/purchase/status", orderController.CheckPurchaseStatus)