1. Poll loop now fully converges with the DB: updated site configs
are refreshed via UpdateSiteConfig, and sites removed from the DB
are evicted from liveState. Previously the loop only added new
sites — config edits via apply were ignored until restart, and
pruned sites kept being checked and alerting.
2. Push monitors now record check history on each heartbeat via
recordCheck. Previously RecordHeartbeat updated state but never
wrote to check_history — push uptime % and sparklines were empty.
3. Groups record a synthetic check per evaluation tick so they get
uptime history and sparklines instead of blank displays.
lerko
