Fix ORM cartesian product warnings

SQLAlchemy v1.4 (Debian Bookworm) annoyingly warns about select statements
that result in a cartesion product of multiple tables. We actually want
cartesion products in all affected cases, so we change "SELECT FROM a,b" to
the equivalent "SELECT FROM a JOIN b ON TRUE".

See https://docs.sqlalchemy.org/en/14/changelog/migration_14.html