No more pkg_resources warnings

This adds initial functionality to render PDF overviews of tracks. I was
pondering to use reportlab and do it completely in Python, but the
effort of doing proper layouting seemed to much. Add to that the fact
that Typst has much nicer typesetting, it seems like a no-brainer to use
it.

See
https://docs.sqlalchemy.org/en/20/changelog/whatsnew_20.html#whatsnew-20-orm-declarative-typing

The Mapped[] annotations help mypy to find the right types for the
instance attributes. Some of the mapped_column() definitions are
superfluous, but I think it's nice to have them explicit.