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- Delete docs/deployment/gitlab.md (superseded by gitea.md)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>

docs/development/code-quality-dashboard-implementation.md

@@ -637,7 +637,7 @@ if args.json:
 
 - Consider adding background job support (Celery/RQ) for long-running scans
 - Add email notifications when violations assigned
-- Consider GitHub/GitLab integration (comment on PRs)
+- Consider Gitea/GitHub integration (comment on PRs)
 - Add historical comparison (violations introduced vs fixed)
 - Consider rule suggestions based on common violations