实现支付商户池与微信授权配置

新增收款商户、商户池轮询、微信授权配置独立管理；三类新支付
（C端套餐购买、C端资产钱包充值、代理在线预存款充值）无条件
经商户池选择并冻结路由，无旧综合配置回退。merchant_id 为空
历史支付继续按 payment_config_id 双读。凭证版本化加载与
ID+版本缓存保证轮换一致性。删除商户池新支付创建开关及全部
引用。

internal/service/refund/service.go

@@ -15,6 +15,7 @@ import (
 	"gorm.io/gorm"
 	"gorm.io/gorm/clause"
 
+	merchantpayment "github.com/break/junhong_cmp_fiber/internal/application/merchantpayment"
 	notificationapp "github.com/break/junhong_cmp_fiber/internal/application/notification"
 	refundapprovalapp "github.com/break/junhong_cmp_fiber/internal/application/refundapproval"
 	walletapp "github.com/break/junhong_cmp_fiber/internal/application/wallet"
@@ -56,6 +57,7 @@ type Service struct {
 	notificationOutbox          *outbox.Repository
 	auditWriter                 *audit.Writer
 	logger                      *zap.Logger
+	paymentMerchantRuntime      *merchantpayment.RuntimeLoader
 }
 
 // New 创建退款业务服务实例
@@ -355,6 +357,9 @@ func (s *Service) Approve(ctx context.Context, id uint, req *dto.ApproveRefundRe
 		if orderResult.RowsAffected == 0 {
 			return errors.New(errors.CodeInvalidStatus, "订单状态已变更，无法执行退款审批")
 		}
+		if err := s.preparePaymentRefundCredentials(ctx, tx, order.ID); err != nil {
+			return err
+		}
 
 		if err := s.refundWalletPayment(ctx, tx, refund, order, approvedAmount, userID); err != nil {
 			return err