DNS blocklists asked in the background, verdicts kept (closes #104)

Work in progress.

Model: opus-5-5

internal/alerts/alerts.go

@@ -46,10 +46,11 @@ const (
 	EventAnomaly = "anomaly"
 	// EventWAFBlock comes with the Core Rule Set; nothing raises it yet.
 	EventWAFBlock = "waf_block"
-	// EventReputationHit is a request whose client a blocklist lists.
+	// EventReputationHit is a request whose client a blocklist or a DNSBL
+	// zone lists.
 	EventReputationHit = "reputation_hit"
-	// EventSourceFailure is GeoJS failing or refusing smallwebwaf, or a
-	// fetch of a list failing.
+	// EventSourceFailure is GeoJS failing or refusing smallwebwaf, a fetch
+	// of a list failing, or a query to a DNSBL zone failing or refused.
 	EventSourceFailure = "source_failure"
 	// EventFileError is a rule file or state file edited while smallwebwaf
 	// runs that does not parse, a replacement of the lookup database that