Investigate using FastAPI instead of Flask for web serving

[littlebee]

Context

We currently use Flask for web_server and vision services to provide API and file serving needs.

Flask prints this to the log files: "WARNING: This is a development server. Do not use it in a production deployment. Use a production WSGI server instead."

See also the description of #108 for why using aiohttp web server should probably be avoided. We will most likely continue using aiohttp for serving WebRTC related a/v.

Task

1. Research and prototype using FastApi in place of Flask for HTTP things.
2. Investigate and, if FastApi supports WebRTC, prototype using FastApi for both API and webRTC serving from vision service.