add flask upgrade to containers on startup

[louking]

maybe instructions at https://docs.docker.com/engine/reference/commandline/compose_run/ are most relevant

"If you want to remove the container after running while overriding the container’s restart policy, use the --rm flag:

$ docker compose run --rm web python manage.py db upgrade

This runs a database upgrade script, and removes the container when finished running, even if a restart policy is specified in the service configuration."

but also see

• https://stackoverflow.com/questions/57556060/how-to-manage-migrations-in-flask-with-docker-compose
• https://stackoverflow.com/questions/55223186/how-to-run-flask-migrate-in-docker
• https://github.com/miguelgrinberg/Flask-Migrate/issues/251