Replace the placeholder MUSICBRAINZ_USER_AGENT env var with
MUSICBRAINZ_OWNER_EMAIL. The User-Agent ("MCMA/<version> ( <contact> )")
is now composed from the fixed app name, the installed package version,
and the operator's contact email — falling back to the project URL when
no email is configured. Also use the same version for the FastAPI app.
Senko-san
olly