Disable records instead of deleting them

A disabled record stays in Jarl with its ID, TTL and comment but is
left out of the zone; the zone file lists it as a comment. Web UI
toggle, jarl record disable|enable, record.disable|enable operations
and API endpoints. Database schema 5.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/render/render.go

@@ -461,6 +461,10 @@ func ZoneFile(s *model.State, z *model.Zone) string {
 		if r.Comment != "" {
 			line += "\t; " + oneLine(r.Comment)
 		}
+		if r.Disabled {
+			// Kept in Jarl, left out of the zone.
+			line = "; disabled: " + line
+		}
 		sb.WriteString(line + "\n")
 	}
 	return sb.String()
@@ -478,7 +482,7 @@ func ZoneContentHash(s *model.State, z *model.Zone) string {
 	h := sha256.New()
 	soa := z.SOA
 	fmt.Fprintf(h, "%s|%d|%s|%s|%d|%d|%d|%d\n", z.Name, z.DefaultTTL, soa.MName, soa.RName, soa.Refresh, soa.Retry, soa.Expire, soa.Minimum)
-	for _, r := range s.ZoneRecords(z.ID) {
+	for _, r := range s.ServedRecords(z.ID) {
 		fmt.Fprintf(h, "%s|%d|%s|%s\n", r.Name, r.EffectiveTTL(z), r.Type, r.Data)
 	}
 	return hex.EncodeToString(h.Sum(nil))