feat: 打手分内部/外部，内部免审核；支持后台指派打手

- worker_users 新增 worker_type（internal/external，迁移 017）
- 内部打手提交验收后自动通过进入待打款（accepted+结算），外部打手保持后台审核
- 打手管理页支持设为内部/外部并显示类型标签
- 新增后台指派打手：未分配/待抢单工单可指定已注册打手，进入其我的订单并冻结押金
- 指派带审计与事件记录，校验打手状态/接单上限/余额押金

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

@@ -2,6 +2,7 @@ import { Router } from 'express'
 
 import {
   acceptAdminWorkOrder,
+  assignAdminWorkOrderToWorker,
   creditAdminWorkerWallet,
   createAdminMockWorkOrder,
   deductAdminWorkOrderPendingDeposit,
@@ -341,6 +342,25 @@ router.put(
   ),
 )
 
+router.post(
+  '/worker-platform/orders/:workOrderId/assign',
+  requireAdminRoles(['admin', 'operator']),
+  createJsonHandler(
+    (req) => assignAdminWorkOrderToWorker(String(req.params.workOrderId || ''), req.body || {}),
+    {
+      successMessage: '已指派打手',
+      errorMessage: '指派打手失败',
+      scope: '[admin/worker-platform/orders/:workOrderId/assign]',
+      audit: (req, data) => ({
+        action: 'work_order_worker_assigned',
+        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']),