[功能]: 将 lbctl 打造成为 LangBot 的独立 Go 控制平面

In addition to the remote workspace entity management in the first phase, we will add the lifecycle management of a locally hosted LangBot running on the same server. When executed on the server, "local" refers to that server. We will not manage other hosts through API, SSH, or remote Docker, nor will we manage the lifecycle of cloud instances.