When a monitor reload was triggered by node auto-registration, the
reloadFunc in server.go recreated the monitor (and its notification
manager) but never re-applied system settings. The new notification
manager started with an empty webhook private CIDR allowlist, causing
webhook notifications to private IPs to fail until the allowlist was
manually re-saved in Settings.
Fix: call router.ReloadSystemSettings() at the end of reloadFunc,
after the new monitor references are set. This re-applies all
persisted system settings — including the webhook CIDR allowlist —
to the freshly created notification manager.
Refs #1507