> Maybe I'll build it one day.
Someone beet you to it [1]
1. https://beets.io/
Beets isn't a daemon like GP asked for. You have to import files manually.
Tons of people have scripted Beets to autotag music as they're downloaded or appear in a directory though. So in that sense it's an automatic, non-manual workflow
I have it tag, convert FLAC to mp3 before importing to Navidrome and moving the FLAC to an archive.