Auto-name conversations

[ErikBjare]

We can already give conversations a name automatically with /rename auto but this should be improved:

• Name conversation automatically with /rename auto
• Don't include date in conversation name, fetch from file/message timestamps.
  • Filesystem metadata not very reliable for this type of thing, but message timestamps are now stored, so should use them.
• Run automatically on save? (if name not already set)

[ErikBjare]

I wrote this script which automatically names all past conversations still using a default randomized name: https://github.com/ErikBjare/gptme/blob/master/scripts/auto_rename_logs.py