feat: 更新后端服务

- agent_handler.go: 新增agent管理接口
- agent_service.go: 扩展agent服务逻辑
- skill_handler.go: 更新skill接口
- chat_service.go: 更新chat服务
- model相关: 新增model仓库和服务
- main.go: 更新路由配置

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

server/internal/service/skill_service.go

@@ -143,7 +143,7 @@ func (s *SkillService) scanSkillsDirectory(basePath string, skillType string) ([
 			SkillType: skillType,
 			SkillDesc: skillInfo.SkillDesc,
 			Path:      skillPath,
-			Status:    "active",
+			Status:    1,
 		}
 
 		skills = append(skills, skill)