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/pages/home/HomeContent.tsx

@@ -7,7 +7,8 @@ import { createContext, useContext, useState, useCallback, useRef, useEffect, us
 import { theme as antTheme, Empty } from 'antd';
 
 import { useAppContext } from '@/components/AppProvider';
-import type { ModelsListResponseBody, TaskInfoItemResponseBody } from '@/services/modules';
+import type { ModelsListResponseBody } from '@/services/modules/models';
+import type { TaskInfoItemResponseBody } from '@/services/modules/task';
 import { LeftPanel } from './components/LeftPanel';
 import { CenterPanel } from './components/CenterPanel';
 import { RightPanel } from './components/RightPanel';