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/components/navbar/AnnouncementDrawer.tsx

@@ -7,7 +7,7 @@ import {useEffect, useState, useCallback} from 'react';
 import {Drawer, Card, Typography, Empty, Tag, Spin, Modal, Tooltip} from 'antd';
 import {NotificationOutlined} from '@ant-design/icons';
 
-import {fetchAnnouncements, type Announcement, AnnouncementListResponse} from '@/services/modules';
+import { fetchAnnouncements, type Announcement, type AnnouncementListResponse } from '@/services/modules/announcement';
 
 const {Text, Paragraph} = Typography;