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/notification/notification-service.ts

@@ -1,4 +1,5 @@
 import { logWarn } from '../../utils/logger.js'
+import type { JsonObject } from '../../types/json.js'
 import {
   getNotificationConfig,
   listEnabledBarkRecipients,
@@ -7,7 +8,6 @@ import {
 import { sendBarkNotification } from './bark-service.js'
 import { sendWpushNotification } from './wpush-service.js'
 
-type JsonObject = Record<string, any>
 type NotificationResult = ReturnType<typeof mapNotificationResult>
 type NotificationInput = {
   title?: string