Add runner execution observability and lifecycle hardening for self-hosted
GitHub Actions runners, including:
- scheduled artifact cleanup job for cached runner tarballs/templates
- workflow_job in_progress handling to mark executions as running
- safer cleanup failure handling and non-functional server fallback
- persisted workflow job HTML URLs with execution "Open" links in UI
- configurable runner group name sync (UI + provisioning + GitHub API)
- webhook events persistence and auto-fix for missing required events
- strict enum/status checks and related model cast/query improvements
Also includes migrations and expanded feature/unit coverage for webhook,
provisioning, cleanup, and runner group/event sync behaviors.
