收紧后端 TypeScript：统一 Json 类型与 TaskContext 契约

关闭 allowJs；集中 JsonObject 定义并替换分散 any 别名；parseTaskContext 返回 TaskContext；任务详情 API 标注 AdminTaskDetailView；测试减少 as any。

apps/backend/src/services/open-91/response.ts

@@ -1,3 +1,4 @@
+import type { JsonObject } from '../../types/json.js'
 import {
   OPEN_91_DEFAULT_FAIL_CODE,
   OPEN_91_SUCCESS_MESSAGE,
@@ -5,8 +6,6 @@ import {
 import { isOpen91FailedTaskStatus } from '../../domain/task-status.js'
 import { normalizeOpen91String } from './payload.js'
 
-type JsonObject = Record<string, any>
-
 export function buildOpen91SuccessResponse(data: unknown, message = OPEN_91_SUCCESS_MESSAGE) {
   return {
     code: 200,