feat: 支持取消指派打手，可重新指派他人

- 后台可取消进行中订单的指派：订单回未分配，冻结押金全额退还，记录事件与审计
- 工单列表新增「取消指派」按钮（带确认弹窗），客服/管理员/运营可用
- 取消后可重新指派给其他打手

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

@@ -3,6 +3,7 @@ import { Router } from 'express'
 import {
   acceptAdminWorkOrder,
   assignAdminWorkOrderToWorker,
+  unassignAdminWorkOrder,
   creditAdminWorkerWallet,
   createAdminMockWorkOrder,
   deductAdminWorkOrderPendingDeposit,
@@ -361,6 +362,22 @@ router.post(
   ),
 )
 
+router.post(
+  '/worker-platform/orders/:workOrderId/unassign',
+  requireAdminRoles(['admin', 'operator', 'support']),
+  createJsonHandler((req) => unassignAdminWorkOrder(String(req.params.workOrderId || '')), {
+    successMessage: '已取消指派',
+    errorMessage: '取消指派失败',
+    scope: '[admin/worker-platform/orders/:workOrderId/unassign]',
+    audit: (req, data) => ({
+      action: 'work_order_worker_unassigned',
+      targetType: 'work_order',
+      targetId: String(req.params.workOrderId || ''),
+      data: data && typeof data === 'object' ? (data as Record<string, unknown>) : {},
+    }),
+  }),
+)
+
 router.delete(
   '/worker-platform/orders/:workOrderId',
   requireAdminRoles(['admin', 'operator']),