fix: add PaymentProvider field to prevent cross-gateway callback attacks

EPay allows users to switch payment methods (e.g. wxpay→alipay) during
checkout, causing callback rejection. Replace fragile blocklist guard
with a PaymentProvider field on TopUp and SubscriptionOrder that
identifies which gateway created the order.

controller/subscription_payment_stripe.go

@@ -84,13 +84,14 @@ func SubscriptionRequestStripePay(c *gin.Context) {
 	}
 
 	order := &model.SubscriptionOrder{
-		UserId:        userId,
-		PlanId:        plan.Id,
-		Money:         plan.PriceAmount,
-		TradeNo:       referenceId,
-		PaymentMethod: model.PaymentMethodStripe,
-		CreateTime:    time.Now().Unix(),
-		Status:        common.TopUpStatusPending,
+		UserId:          userId,
+		PlanId:          plan.Id,
+		Money:           plan.PriceAmount,
+		TradeNo:         referenceId,
+		PaymentMethod:   model.PaymentMethodStripe,
+		PaymentProvider: model.PaymentProviderStripe,
+		CreateTime:      time.Now().Unix(),
+		Status:          common.TopUpStatusPending,
 	}
 	if err := order.Insert(); err != nil {
 		c.JSON(http.StatusOK, gin.H{"message": "error", "data": "创建订单失败"})