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/presenter.go

@@ -56,6 +56,8 @@ func (row orderRow) toAdminDTO() OrderDTO {
 		Status:                    row.Status,
 		HandoffStatus:             row.HandoffStatus,
 		SettlementStatus:          row.SettlementStatus,
+		RefundStatus:              row.RefundStatus,
+		RefundAmountCent:          row.RefundAmountCent,
 		AdminActions:              adminActionsForOrder(row.RentalOrder),
 		CreatedAt:                 row.CreatedAt,
 		UpdatedAt:                 row.UpdatedAt,