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

frontend/src/layouts/AdminLayout.vue

@@ -83,6 +83,12 @@ const allNavGroups: NavGroup[] = [
     children: [
       { label: '用户管理', to: adminPath('users'), icon: User, permission: 'user:view' },
       { label: '订单管理', to: adminPath('orders'), icon: Tickets, permission: 'order:view' },
+      {
+        label: '退款审核',
+        to: adminPath('orders/refund-review'),
+        icon: Money,
+        permission: 'order:close',
+      },
       { label: '商品管理', to: adminPath('listings'), icon: Shop, permission: 'listing:view' },
       {
         label: '商品审核',