接单工单支持置顶，抢单大厅优先展示

- 新增 work_orders.pinned_at 字段与迁移
- 管理端对已发布（待抢单）订单提供置顶/取消置顶操作，置顶订单带标记
- 抢单大厅按置顶时间优先排序，打手端卡片展示置顶标签

apps/frontend/src/pages/worker/WorkerHallPage.tsx

@@ -1,4 +1,4 @@
-import { ClockCircleOutlined, ReloadOutlined, SearchOutlined, TrophyOutlined } from '@ant-design/icons'
+import { ClockCircleOutlined, PushpinOutlined, ReloadOutlined, SearchOutlined, TrophyOutlined } from '@ant-design/icons'
 import { useQuery, useQueryClient } from '@tanstack/react-query'
 import {
   Alert,
@@ -367,6 +367,11 @@ export default function WorkerHallPage() {
                     {/* 卡片头部: 分类 + 拼单/时限标签 + 订单号 */}
                     <div className="worker-hall-mobile-card-top">
                       <div className="worker-hall-mobile-card-tags">
+                        {order.pinnedAt ? (
+                          <Tag color="gold" icon={<PushpinOutlined />} className="worker-hall-mobile-tag">
+                            置顶
+                          </Tag>
+                        ) : null}
                         {order.categoryName ? (
                           <Tag color="blue" className="worker-hall-mobile-tag">
                             {order.categoryName}
@@ -610,6 +615,11 @@ export default function WorkerHallPage() {
                     return (
                       <article key={order.workOrderId} className="worker-hall-card">
                         <div className="worker-hall-card-title">
+                          {order.pinnedAt ? (
+                            <Tag color="gold" icon={<PushpinOutlined />} className="worker-hall-pinned-tag">
+                              置顶
+                            </Tag>
+                          ) : null}
                           <strong
                             className="worker-hall-card-title-text"
                             title={order.productName || '未命名商品'}