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/backend/src/routes/admin/worker-platform.ts

@@ -23,6 +23,7 @@ import {
   listAdminWorkerUsers,
   listAdminWorkOrders,
   markAdminWorkOrderProblem,
+  pinAdminWorkOrder,
   publishAdminWorkOrder,
   reviewAdminWorkerFinanceRequest,
   resolveAdminProblemWorkOrder,
@@ -450,6 +451,25 @@ router.post(
   }),
 )
 
+router.post(
+  '/worker-platform/orders/:workOrderId/pin',
+  requireAdminRoles(['admin', 'operator', 'support']),
+  createJsonHandler(
+    (req) => pinAdminWorkOrder(String(req.params.workOrderId || ''), req.body || {}),
+    {
+      successMessage: '置顶状态已更新',
+      errorMessage: '更新置顶状态失败',
+      scope: '[admin/worker-platform/orders/:workOrderId/pin]',
+      audit: (req, data) => ({
+        action: 'work_order_pin_toggled',
+        targetType: 'work_order',
+        targetId: String(req.params.workOrderId || ''),
+        data: data && typeof data === 'object' ? (data as Record<string, unknown>) : {},
+      }),
+    },
+  ),
+)
+
 router.get(
   '/worker-platform/orders/:workOrderId/sharing',
   requireAdminRoles(['admin', 'operator', 'support']),