feat: Simple WebGUI for chat

[tronba]

Problem I would love for others in my household to chat with my Jan install using a simple WebGUI.

Success Criteria A simple WebGUI to chat with the same model as is loaded in the client GUI. WebGUI should preferably not have any controls (be able to change config, download, or select model). WebGUI should show what model is loaded. WebGUI feature should be able to turn on/off in client GUI. WebGUI port should be possible to change in client GUI. WebGUI chat history should not be visible to others and not shown in client GUI. The client would have to deal with the possibility of multiple simultaneous chats, maybe possible to do with a timeslot or waitlist system?