退款审核功能：待交接取消不再自动退款，改为客服审核后原路退回

- 租客在待交接状态取消订单不再自动退款，改为 refund_status=pending_review
- 新增退款审核页面 /admin/orders/refund-review，客服可逐个审核
- 新增 POST /refund/approve 通过退款、POST /refund/reject 驳回退款
- 新增 GET /orders/refund-pending 查询待审核退款订单列表
- 优化状态标签表述：已取消→租客已取消、已关闭→客服已关闭、异常→客服介入
- 新增 refund_status: pending_review 及其前端标签「待客服审核退款」
- AdminOrderDetailView 退款状态改用统一 refundStatusLabel

backend/internal/modules/order/service.go

@@ -226,6 +226,33 @@ func (s *Service) AdminRefundStatus(ctx context.Context, orderID uint64) (*Refun
 	return s.repo.AdminRefundStatus(ctx, orderID)
 }
 
+func (s *Service) AdminApproveRefund(ctx context.Context, orderID uint64) error {
+	if s.repo == nil {
+		return ErrDependencyUnavailable
+	}
+	if orderID == 0 {
+		return ErrOrderCannotComplete
+	}
+	return s.repo.AdminApproveRefund(ctx, orderID)
+}
+
+func (s *Service) AdminRejectRefund(ctx context.Context, orderID uint64) error {
+	if s.repo == nil {
+		return ErrDependencyUnavailable
+	}
+	if orderID == 0 {
+		return ErrOrderCannotComplete
+	}
+	return s.repo.AdminRejectRefund(ctx, orderID)
+}
+
+func (s *Service) ListPendingRefund(ctx context.Context) ([]OrderDTO, error) {
+	if s.repo == nil {
+		return nil, ErrDependencyUnavailable
+	}
+	return s.repo.ListPendingRefund(ctx)
+}
+
 func (s *Service) FindForUser(ctx context.Context, userID uint64, orderID uint64) (*OrderDTO, error) {
 	if s.repo == nil {
 		return nil, ErrDependencyUnavailable