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/services/modules/index.ts

@@ -1,63 +0,0 @@
-// ============================================================
-// API 模块统一导出
-// ============================================================
-
-export {
-    fetchAnnouncements,
-    type Announcement,
-    type AnnouncementType,
-    type AnnouncementListResponse,
-} from './announcement';
-
-export {
-    AuthAPI,
-    type SendSMSRequestBody,
-    type RegisterRequestBody,
-    type RegisterResponseBody,
-    type LoginRequestBody,
-    type LoginResponseBody,
-    type RefreshTokenRequestBody,
-    type RefreshTokenResponseBody,
-    type UserInfoBody,
-    type ChangePasswordRequestBody,
-    type UsePhoneResetPasswordRequestBody,
-} from './auth';
-
-export {
-    fetchBanners,
-    type Banner,
-    type BannerListResponse,
-} from './banner';
-
-export {
-    ModelAPI,
-    MODEL_CATEGORIES,
-    MODEL_CATEGORY_LABELS,
-    CATEGORY_SLUG_MAP,
-    resolveCategoryLabel,
-    toCategorySlug,
-    type ModelsListReqeustParams,
-    type ModelsListResponseBody,
-    type ModelInfoRequestParams,
-    type ModelInfoResponseBody,
-    type ModelCategoryStringEnum,
-    type ParamSchemaItem,
-} from './models';
-
-export {
-    TaskAPI,
-    OutputTypeMap,
-    TaskStatusMap,
-    type OutputTypeString,
-    type TaskStatusString,
-    type TaskListRequestParams,
-    type CreatTaskRequestBody,
-    type ExportTaskCSVParams,
-    type ContentItem,
-    type ImageUiParams,
-    type VideoUiParams,
-    type AudioUiParams,
-    type TaskInfoItemResponseBody,
-    type TaskInfoDataResponseBody,
-    type TaskStatusResponseBody,
-} from './task';