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/auth/auth.module.ts

@@ -12,7 +12,7 @@ import { JwtStrategy } from './jwt.strategy';
     JwtModule.registerAsync({
       useFactory: (config: ConfigService) => ({
         secret: config.get('JWT_SECRET'),
-        signOptions: { expiresIn: config.get('JWT_EXPIRES_IN') || '2h' },
+        signOptions: { expiresIn: config.get('JWT_EXPIRES_IN') || '7d' },
       }),
       inject: [ConfigService],
     }),

backend/src/modules/auth/auth.service.ts

@@ -84,8 +84,8 @@ export class AuthService {
   private generateTokens(userId: number) {
     const payload = { sub: userId };
     return {
-      accessToken: this.jwtService.sign(payload, { expiresIn: '2h' }),
-      refreshToken: this.jwtService.sign(payload, { expiresIn: '7d' }),
+      accessToken: this.jwtService.sign(payload, { expiresIn: '7d' }),
+      refreshToken: this.jwtService.sign(payload, { expiresIn: '30d' }),
     };
   }
 }