feat: admin可编辑内置专家 + agent列表Tab分组

- /login/admin 登录时自动赋予 admin 角色，允许编辑内置专家
- agent列表页新增「全部」(内置+已发布) 和「自己的」两个Tab

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.gitignore

@@ -60,6 +60,7 @@ offline-backend-20260512/skills/
 offline-backend-20260512/wheelhouse/
 offline-backend-20260512/backend/.deer-flow/data/*.db
 offline-backend-20260512/backend/.deer-flow/data/*.db-*
+offline-backend-20260512/backend/.deer-flow/*
 offline-backend-20260512/start_backend.sh
 offline-backend-20260512/stop_backend.sh
 offline-backend-20260512/check_backend.sh