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/lib/Zonemaster/Engine/Validation.pm

@@ -0,0 +1,94 @@
+package Zonemaster::Engine::Validation;
+
+use v5.16.0;
+use warnings;
+
+use version; our $VERSION = version->declare("v1.0.0");
+
+use Exporter 'import';
+BEGIN {
+    our @EXPORT_OK = qw[
+      validate_ipv4
+      validate_ipv6
+    ];
+    our %EXPORT_TAGS = ( all => \@EXPORT_OK );
+
+    ## no critic (Modules::ProhibitAutomaticExportation)
+    our @EXPORT = qw[ 
+      validate_ipv4
+      validate_ipv6
+    ];
+}
+
+use Readonly;
+use Net::IP::XS;
+
+use Zonemaster::Engine::Constants qw[:ip];
+
+Readonly our $IPV4_RE => qr/^[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}$/;
+Readonly our $IPV6_RE => qr/^[0-9a-f:]*:[0-9a-f:]+(:[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3})?$/i;
+
+sub validate_ipv4 {
+    my ( $ip ) = @_;
+
+    if ( defined $ip and $ip ne '') {
+        if ( Net::IP::XS->new( $ip ) ) {
+            if ( Net::IP::XS::ip_is_ipv4( $ip ) and $ip =~ /($IPV4_RE)/ ) {
+                return 1;
+            }
+        }
+    }
+
+    return 0;
+}
+
+sub validate_ipv6 {
+    my ( $ip ) = @_;
+
+    if ( defined $ip and $ip ne '' ) {
+        if ( Net::IP::XS->new( $ip ) ) {
+            if ( Net::IP::XS::ip_is_ipv6( $ip ) and $ip =~ /($IPV6_RE)/ ) {
+                return 1;
+            }
+        }
+    }
+
+    return 0;
+}
+
+1;
+
+=head1 NAME
+
+Zonemaster::Engine::Validation - validation functions for other Zonemaster modules
+
+=head1 SYNOPSIS
+
+    use Zonemaster::Engine::Validation qw( validate_ipv4 validate_ipv6 );
+    my $ip_is_valid = validate_ipv4( $ip_address );
+
+=head1 EXPORTED FUNCTIONS
+
+=over
+
+=item validate_ipv4
+
+    my $ip_is_valid = validate_ipv4( $ip_address );
+
+Checks if the given IP address is a valid IPv4 address.
+
+Takes a string (IP address).
+
+Returns a boolean.
+
+=item validate_ipv6
+
+    my $ip_is_valid = validate_ipv6( $ip_address );
+
+Checks if the given IP address is a valid IPv6 address.
+
+Takes a string (IP address).
+
+Returns a boolean.
+
+=back