Better demo front-end

We do not want to maintain any production front-end, but we have limitations on our current langserve playground demo front-end that makes testing and interactions with our API's not optimal. This would not be meant as something to copy and deploy in production and should be as bare bones as we can get away with.

Simple chat, where you can see sources listed No chat history No system prompts Only a display Loads of warnings that this is for testing and not to be distributed Some reporting functionality for testers indicate issues. Would require an endpoint for receiving repports - see other issue