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

modules/router/dhcp.nix

@@ -71,6 +71,17 @@ in
               name = "domain-name-servers";
               data = l.ipv4.address;
             }
+          ]
+          # The local domain: clients use it for short names (nas -> nas.home...).
+          ++ lib.optionals (cfg.dns.domain != null) [
+            {
+              name = "domain-name";
+              data = cfg.dns.domain;
+            }
+            {
+              name = "domain-search";
+              data = cfg.dns.domain;
+            }
           ];
         }) dhcpLans;
       };