Add WireGuard, DNS and more to the web UI and router-setup

Web UI: a WireGuard page (tunnels, peers, keys made on the router, client
configs with a QR code, import of wg-quick configs, live status), a DNS page
(records, wildcards, forward zones), interface dropdowns with VLAN devices,
IPv6 options and a local domain. router-setup asks about VLANs, IPv6 and
the domain. The router publishes its own name in DNS and hands the local
domain to DHCP clients; wg and jq are on the router. Includes a script
that takes over antigua's tunnels.

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

pkgs/router-webui/templates/layout.html

@@ -15,6 +15,8 @@
     <a href="/">Overview</a>
     <a href="/network">Network</a>
     <a href="/dhcp">DHCP</a>
+    <a href="/dns">DNS</a>
+    <a href="/wireguard">WireGuard</a>
     <a href="/update">Update</a>
     <a href="/advanced">Advanced</a>
     <form method="post" action="/logout"><input type="hidden" name="csrf" value="{{.CSRF}}"><button class="link">Log out</button></form>