Some minor fixes

• Please check this box if this contribution uses AI-generated content (including content generated by GitLab Duo features) as outlined in the GitLab DCO & CLA

• No login is required, all images are public
• Simplify docker exec command
  docker-compose can do exec without needing an extra step.
• Some settings in GitLab moved around
  The settings for {im,ex}ports are no longer located in the section Visibility
• Use the container hostnames for both in congregate
  The template congregate config had one container hostname and one ip-address. These ip-addresses are not guaranteed to be the same across machines. Therefore, use the container hostname in both cases.
• Should not use TLDRs for local stuff
  the compose file specifies gitlab-src-local.com as hostnames. One should not use globaly valid names for exclusively local stuff.