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/services/worker-platform/admin-service.ts

@@ -6,6 +6,7 @@ import {
   acceptWorkOrderAndSettle,
   addWorkerWalletCredit,
   assignWorkOrderToWorker,
+  unassignWorkOrder,
   countWorkerAcceptedOrders,
   countWorkerActiveOrders,
   countWorkCategoryUsages,
@@ -1146,6 +1147,43 @@ export async function acceptAdminWorkOrder(workOrderId: number | string) {
   return { order: mapWorkOrderAdmin(updated || workOrder) }
 }
 
+export async function unassignAdminWorkOrder(workOrderId: number | string) {
+  const workOrder = await getRequiredWorkOrder(workOrderId)
+  if (
+    workOrder.status !== WORK_ORDER_STATUS.IN_PROGRESS ||
+    !workOrder.assigned_worker_id
+  ) {
+    throw createHttpError('只有进行中且已指派打手的订单可以取消指派', {
+      statusCode: 409,
+      errorCode: 'work_order_unassign_status_invalid',
+    })
+  }
+  const now = nowIso()
+  const { order: updated, failureReason } = await unassignWorkOrder({
+    workOrderId: workOrder.id,
+    now,
+  })
+  if (failureReason === 'work_order_not_in_progress') {
+    throw createHttpError('订单状态已变化，无法取消指派', {
+      statusCode: 409,
+      errorCode: 'work_order_unassign_status_invalid',
+    })
+  }
+  if (failureReason === 'work_order_no_worker') {
+    throw createHttpError('该订单未指派打手', {
+      statusCode: 409,
+      errorCode: 'work_order_unassign_no_worker',
+    })
+  }
+  if (!updated) {
+    throw createHttpError('取消指派失败，订单状态可能已变化', {
+      statusCode: 409,
+      errorCode: 'work_order_unassign_conflict',
+    })
+  }
+  return { order: mapWorkOrderAdmin(updated) }
+}
+
 export async function getAdminWorkerPlatformSummary() {
   const [pendingWorkers, pendingMaterial, openOrders, inProgressOrders] = await Promise.all([
     listWorkerUsers({ page: 1, pageSize: 1, status: 'pending_review' }),