Add also-notify support for BIND domains.conf generation

Extend catz.yaml config with a bind-conf section mapping catalog names
to also-notify IP lists. Zones in catalogs with also-notify configured
get an also-notify directive in the generated domains.conf. IPs are
deduplicated and sorted when a zone belongs to multiple catalogs.

main.go

@@ -72,7 +72,7 @@ func main() {
 	}
 
 	if *bindConf != "" {
-		if err := writeBindConf(*bindConf, entries); err != nil {
+		if err := writeBindConf(*bindConf, entries, cfg); err != nil {
 			fmt.Fprintf(os.Stderr, "error: %s\n", err)
 			hasErrors = true
 		} else {