feat: admin back-office system + AI assistant with action commands

- Admin analytics (recharts charts, overview stats, trend analysis, time range selector)
- Admin permissions (AdminRole/AdminUser models, role CRUD, permission catalog)
- Admin system config (site/AI/member category tabs, per-key save)
- Admin operations (Banner CRUD, push notification send/delete)
- Admin user management (table, search, create/edit, ban/delete)
- Admin layout (custom top bar with branding + sidebar, admin AI assistant)
- Admin login (adminToken localStorage, adminInfo display)
- Admin AI assistant (purple '运营助手', context-aware prompts, action commands)
- Public AI assistant Phase B (action commands: navigate, setModel, startChat, openSkill, setParameter)
- Assistant context mapping + action executor
- Skills API fix: tags parsing fallback (JSON.parse → split)
- Sandbox crash fix: curScene fallback system prompt
- JWT token expiration: access 2h→7d, refresh 7d→30d, admin 8h→7d
- i18n: assistant-related translations (zh/en)
- PM2 ecosystem config for process management
- AI assistant login prompt fix: admin uses getAdminToken(), public uses apiFetch with token refresh

backend/src/modules/admin/admin.module.ts

@@ -3,12 +3,16 @@ import { JwtModule } from '@nestjs/jwt';
 import { AdminController } from './admin.controller';
 import { AdminService } from './admin.service';
 import { AdminGuard } from './admin.guard';
+import { AnalyticsController } from './analytics.controller';
+import { SettingsController } from './settings.controller';
+import { OperationsController } from './operations.controller';
+import { UsersController } from './users.controller';
 import { CoursesModule } from '../courses/courses.module';
 import { AuthModule } from '../auth/auth.module';
 
 @Module({
   imports: [CoursesModule, AuthModule],
-  controllers: [AdminController],
+  controllers: [AdminController, AnalyticsController, SettingsController, OperationsController, UsersController],
   providers: [AdminService, AdminGuard],
   exports: [AdminService],
 })