move audio writing to server from client

[ezavesky]

I would like the server to be responsible for logging new audio files to disk instead of the client so that it can intercept incoming requests from both the file API as well as WebSocket. Additionally, this utilizes the EOS marker that clearly indicates that the server should stop recording a stream.

• transplant code using this function into something around this point

This will be a self-completed issue, but seeking opinion before execution.