Publish DHCP clients' names in DNS

router-webui leases-dns reads Kea's leases and publishes <name>.<domain>
with reverse records in the running Unbound (router.dns.dynamicLeases).
Names the configuration publishes are never taken over; a client's name
is cut to its first label and kept inside the local domain; of two
clients the newer lease wins. The DNS page switches it on and shows what
is published and what was skipped; router-setup enables it with a domain.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01AeFqV9dZrK6nipHkPfyM4F

pkgs/router-webui/main.go

@@ -7,6 +7,7 @@
 //	router-webui [-listen :443] [-config DIR] [-state DIR] [-leases FILE]
 //	router-webui passwd FILE   (reads the new password from stdin)
 //	router-webui unbundle FILE DIR   (stages an update bundle; FILE - is stdin)
+//	router-webui leases-dns          (publishes DHCP clients' names in Unbound)
 package main
 
 import (
@@ -51,6 +52,10 @@ var embedded embed.FS
 var assets fs.FS = embedded
 
 func main() {
+	if len(os.Args) > 1 && os.Args[1] == "leases-dns" {
+		leasesDNS(os.Args[2:])
+		return
+	}
 	if len(os.Args) == 3 && os.Args[1] == "passwd" {
 		if err := setPassword(os.Args[2]); err != nil {
 			log.Fatal(err)