Show server status in front end

[davidborland]

Currently just have a static Loading... message. Instead show a message with some animation (spinner or animated ellipse or other) that shows what step the backend is in, e.g. Checking guardrails -> checking for predefined responses -> generating response, etc.

I presume this would entail adding a status endpoint to the backend, and then polling that endpoint, so will need some coordination between @mbwatson and @StevenGuo42. Assigning to @mbwatson though.

[davidborland]

@StevenGuo42 should look into using streaming events for this: https://python.langchain.com/docs/concepts/streaming/#streaming-apis