huggingface/chat-ui ? reverse-engineered prompt

Build me a web app like HuggingChat, a clean AI chat interface where people can sign in, start new conversations, see their chat history, and talk to any OpenAI compatible model endpoint.

I want it to look polished and modern, with a sidebar for chats, a main message thread, model switching, basic settings, and a nice responsive mobile layout. It should save chats and user settings in a database, and work locally for development with simple environment variables so I can point it at a model server like Hugging Face Router, Ollama, or another OpenAI style API.

If it makes sense, include a simple theming setup so the app name, logo, and colors can be changed easily. Make sure the app is ready to run, easy to launch, and feels like a real production chat product. If you need current docs for anything, look them up online.