Site.ArtifactRevisionHash / ArtifactsDeployedAt (nullable, migration
AddSiteArtifactRevision) so the Sites page can tell whether a site's
system-wide artifacts are current. Not transported. Adds the
GetDeployedRevisionHashesAsync projection for the fleet-wide staleness batch.
Claude-Session: https://claude.ai/code/session_01Y5ef34iUUMjmwnMpL9xgmB
Joseph Doherty