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/idn.t

@@ -0,0 +1,30 @@
+use Test::More;
+use Test::Fatal;
+use Encode;
+use Devel::Peek;
+use utf8;
+
+BEGIN { use_ok( "Zonemaster::LDNS" => qw[:all] ) }
+
+no warnings 'uninitialized';
+if (exception {to_idn("whatever")} =~ /libidn2 not installed/) {
+    ok(!has_idn(), 'No IDN');
+    done_testing;
+    exit;
+}
+
+ok(has_idn(), 'Has IDN');
+my $encoded = to_idn( 'annaröd.se' );
+is( $encoded, 'xn--annard-0xa.se', 'One name encoded right' );
+
+my @before = ('annaröd.se', 'rindlöw.se', 'räksmörgås.se', 'nic.中國', 'iis.se');
+my @many = to_idn @before;
+is_deeply(
+    \@many,
+    [qw( xn--annard-0xa.se xn--rindlw-0xa.se xn--rksmrgs-5wao1o.se nic.xn--fiqz9s iis.se )],
+    'Many encoded right'
+);
+
+like( exception { to_idn( "ö" x 63 ) }, qr/IDN2_PUNYCODE_/i, 'croaks on IDN encoding failures' );
+
+done_testing;