refactor(admin): 合并管理后台并移除 apps/agent

- 平台与代理共用 apps/admin，统一登录 manage/auth/login
- 按 userType 展示菜单，修复 token 循环跳转
- 删除独立 apps/agent 前端工程

Co-authored-by: Cursor <cursoragent@cursor.com>

apps/api/src/domains/identity/auth.service.ts

@@ -22,6 +22,19 @@ export class AuthService {
     private config: ConfigService,
   ) {}
 
+  /** 平台管理员 / 代理统一登录（按 userType 签发对应 JWT） */
+  async staffLogin(username: string, password: string) {
+    const user = await this.prisma.user.findUnique({
+      where: { username },
+      select: { userType: true },
+    });
+    if (!user || (user.userType !== 'ADMIN' && user.userType !== 'AGENT')) {
+      throw new UnauthorizedException('Invalid credentials');
+    }
+    const portal = user.userType === 'ADMIN' ? 'admin' : 'agent';
+    return this.login(username, password, portal);
+  }
+
   async login(username: string, password: string, portal: 'player' | 'admin' | 'agent') {
     const user = await this.prisma.user.findUnique({
       where: { username },