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-engine/t/validation.t

@@ -0,0 +1,49 @@
+use v5.16.0;
+use warnings;
+
+use Test::More;
+use Test::Differences;
+
+BEGIN { 
+    use_ok( 'Zonemaster::Engine::Validation' ), qw( validate_ipv4 validate_ipv6 )
+}
+
+subtest 'validate_ipv4()' => sub {
+    my @ipv4_addresses = ( '127.0.0.1', '1.1.1.1' );
+    subtest 'Valid IPv4 addresses' => sub {
+        foreach my $ip ( @ipv4_addresses ) {
+            my $ip_is_valid = validate_ipv4( $ip );
+            eq_or_diff $ip_is_valid, 1, "$ip is a valid IPv4 address";
+        }
+    };
+
+    my @inv_ipv4_addresses = ( 'fe80::127:0:0:1', 'abcd', '@bcd3', 'a.b.c.d', '', undef );
+    subtest 'Invalid IPv4 addresses' => sub {
+        foreach my $ip ( @inv_ipv4_addresses ) {
+            my $ip_is_valid = validate_ipv4( $ip );
+            $ip = 'undef' unless defined($ip);
+            eq_or_diff $ip_is_valid, 0, "$ip is an invalid IPv4 address";
+        }
+    };
+};
+
+subtest 'validate_ipv6()' => sub {
+    my @ipv6_addresses = ( 'fe80::127:0:0:1', '::1:1:1:1' );
+    subtest 'Valid IPv6 addresses' => sub {
+        foreach my $ip ( @ipv6_addresses ) {
+            my $ip_is_valid = validate_ipv6( $ip );
+            eq_or_diff $ip_is_valid, 1, "$ip is a valid IPv6 address";
+        }
+    };
+
+    my @inv_ipv6_addresses = ( '127.0.0.1', 'wxyz', 'wxyz!', '::w:x:y:z', '', undef );
+    subtest 'Invalid IPv6 addresses' => sub {
+        foreach my $ip ( @inv_ipv6_addresses ) {
+            my $ip_is_valid = validate_ipv6( $ip );
+            $ip = 'undef' unless defined($ip);
+            eq_or_diff $ip_is_valid, 0, "$ip is an invalid IPv6 address";
+        }
+    };
+};
+
+done_testing;