refactor: 消除占位页面 + 删除 barrel 导出 — 页面集中注册 + 直接导入

- 删除 8 个占位页面文件（Account/Vip/Recharge/Billing/Orders/Projects/Quota/ComplianceAssets）
- PageDispatcher: PAGE_MAP 支持无组件页面自动渲染 PlaceholderPage
- 新增页面只需在 PAGE_MAP 加一行配置，无需创建独立文件
- 删除 services/modules/index.ts barrel，13 个文件改为直接导入
- IDE 跳转到定义一步到位，import 自文档化
- TypeScript 编译零错误

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/hooks/use-api.ts

@@ -14,18 +14,9 @@
 
 import {useMemo} from 'react';
 import {useAppContext} from '@/components/AppProvider';
-import {
-    TaskAPI,
-    ModelAPI,
-    fetchBanners,
-    MODEL_CATEGORY_LABELS,
-    type TaskListRequestParams,
-    type TaskInfoItemResponseBody,
-    type CreatTaskRequestBody,
-    type ModelsListResponseBody,
-    type Banner,
-    type ModelCategoryStringEnum,
-} from '@/services/modules';
+import { TaskAPI, type TaskListRequestParams, type TaskInfoItemResponseBody, type CreatTaskRequestBody } from '@/services/modules/task';
+import { ModelAPI, MODEL_CATEGORY_LABELS, type ModelsListResponseBody, type ModelCategoryStringEnum } from '@/services/modules/models';
+import { fetchBanners, type Banner } from '@/services/modules/banner';
 import {useAsyncData, UseAsyncDataReturn, useAsyncMutation} from './use-async';
 
 // ============================================================