refactor: remove GitLab CI config and docs after full Gitea migration

- Delete .gitlab-ci.yml (replaced by .gitea/workflows/ci.yml)
- Delete docs/deployment/gitlab.md (superseded by gitea.md)
- Update audit rules to reference .gitea/workflows/*.yml
- Update validate_audit.py to check Gitea CI paths
- Clean up GitLab references in gitea.md, mkdocs.yml, .dockerignore
- Mark IPv6 AAAA records as completed in hetzner docs

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

.dockerignore

@@ -3,7 +3,6 @@
 !.env.example
 .git
 .gitea
-.gitlab-ci.yml
 __pycache__
 *.pyc
 *.pyo