feat: add full Zonemaster stack with Docker and Spanish UI

- Clone all 5 Zonemaster component repos (LDNS, Engine, CLI, Backend, GUI)
- Dockerfile.backend: 8-stage multi-stage build LDNS→Engine→CLI→Backend
- Dockerfile.gui: Astro static build served via nginx
- docker-compose.yml: backend (internal) + frontend (port 5353)
- nginx.conf: root redirects to /es/, /api/ proxied to backend
- zonemaster-gui/config.ts: defaultLanguage set to 'es' (Spanish)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

zonemaster-ldns/t/load_zonefile.t

@@ -0,0 +1,15 @@
+use Test::More;
+use Test::Fatal;
+
+use strict;
+use warnings;
+
+BEGIN { use_ok("Zonemaster::LDNS" => qw(load_zonefile))}
+
+my @rrs = load_zonefile("t/example.org");
+is(scalar(@rrs), 16, 'All records loaded');
+is($rrs[0]->type, 'SOA', 'SOA record first');
+is($rrs[-1]->type, 'A', 'A record last');
+is(lc($rrs[-1]->name), 'spencer.example.org.', 'Expected name last');
+
+done_testing();