Revert to backup lets you delete tab password

[JoeyRubas]

Problem encountered at UChicago Apda Tournament spring 2025. Revert to the first backup ends up deleting the tab password, locking out the tab director.

I haven't tested it, but my theory is it's a result of the backup call at the start of the handle in the initalize_tournament management command.

    def handle(self, *args, **options):
        backup_round("before_new_tournament")
        self.stdout.write("Clearing data from database")
        try:
            call_command("flush", interactive=False)
        except (IOError, os.error) as why:
            self.stdout.write("Failed to clear database")
            print(why)
            sys.exit(1)

This is the intended behavior when making a new tournament (when one already exists), but when ran on initialization I think it results in the creation of a backup that was created before the tab password was put in the database, and thus reverting to that backup locks tab out.