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.service.ts

@@ -11,7 +11,10 @@ export class AdminService {
   ) {}
 
   async login(username: string, password: string) {
-    const admin = await this.prisma.adminUser.findUnique({ where: { username } });
+    const admin = await this.prisma.adminUser.findUnique({
+      where: { username },
+      include: { role: true },
+    });
     if (!admin || admin.status !== 'ACTIVE') {
       throw new UnauthorizedException('管理员账号不可用');
     }
@@ -28,10 +31,10 @@ export class AdminService {
 
     const token = this.jwtService.sign(
       { sub: admin.id, type: 'admin' },
-      { expiresIn: '8h' },
+      { expiresIn: '7d' },
     );
 
-    return { token, id: admin.id, username: admin.username, role: admin.role };
+    return { token, id: admin.id, username: admin.username, role: admin.role?.name };
   }
 
   async getDashboard() {