I've done a similar thing with https://github.com/DimitriGilbert/LiteChat/ but for features and not really UI ^^ you should give it a spin, it might give you ideas definitely going to try yours :)

edit: ooooh maaan... do you think you could add https://openrouter.ai/ key support please ? And for a bit of return on experience, you should absolutely use something like the vercel AI-SDK (or similar, i know there are more) to have support for many providers !