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/regression.t

@@ -0,0 +1,17 @@
+use Test::More;
+use Test::Fatal;
+
+use strict;
+use warnings;
+
+BEGIN { use_ok("Zonemaster::LDNS")}
+
+SKIP: {
+    skip 'no network', 2 unless $ENV{TEST_WITH_NETWORK};
+
+    my $s = Zonemaster::LDNS->new( '8.8.8.8' );
+    isa_ok( $s, 'Zonemaster::LDNS' );
+    like( exception { $s->query( 'xx--example..', 'A' ) }, qr/Invalid domain name: xx--example../, 'Died on invalid name');
+}
+
+done_testing;