The v1.69.0 caching refactor replaced Redis pub/sub with a global 30s
client polling interval. Live monitoring widgets (health-monitoring,
Dashdot, dns-hole) that previously refreshed every 5s were stuck at 30s.
Adds a typed WidgetRefetchInterval preset (fiveSeconds | never) to
WidgetDefinition. Widgets that need faster polling set fiveSeconds;
widgets that don't need polling set never (fetch on mount only, manual
refresh via context menu). Absence = global 30s default.
nine widgets get fiveSeconds (live monitoring)
sixteen widgets get never (slow data, mount-only)
remaining widgets use the 30s default
Also removes inline refetchInterval from docker widget component.
Fixes#6268
ajnart
