Two things you could try:
(1) In the same directory as your docker-compose.yml file run this command:
sudo docker-compose exec -u www-data www drush theme:enable gin
That will attempt to re-enable Gin via the command line.
If that doesn’t work…
(2) Try uninstalling farm_ui_theme with this:
sudo docker-compose exec -u www-data www drush pm-uninstall farm_ui_theme
That will attempt to uninstall the farm_ui_theme module. Note that it will prompt you to uninstall farm_ui as well, which is OK.
If that works, then you should be able to log back into the site, re-enable Gin manually (via /admin/appearance), then you can re-enable farm_ui (which will also enable farm_ui_theme) with:
sudo docker-compose exec -u www-data www drush pm-uninstall farm_ui
Hope one of those works! 