- Add /diagnostics endpoint for system health overview
- Add external health worker for monitoring Gitea, Woodpecker, Registry
- Add health check methods to Gitea and Woodpecker clients
- Remove hardcoded fallback projects (pantheon, aeries)
- Add diagnostics domain types and service layer
- Add comprehensive tests for diagnostics handler and service
- Fix tests to use registered test project instead of hardcoded one
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
