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/pod-coverage.t

@@ -0,0 +1,51 @@
+use Test::More;
+
+use 5.14.2;
+use strict;
+use warnings;
+
+use Zonemaster::Engine;
+use File::Find;
+
+eval { require Pod::Coverage };
+if ( $@ ) {
+    plan skip_all => "Need Pod::Coverage to run these tests.";
+    exit( 0 );
+}
+
+my @modules;
+
+find(
+    sub {
+        if ( $File::Find::name =~ m|lib/(.*)\.pm| ) {
+            my $name = $1;
+            $name =~ s|/|::|g;
+
+            push @modules, $name;
+        }
+    },
+    'lib'
+);
+
+foreach my $name ( @modules ) {
+    next if $name =~ q{Zonemaster::Engine::Constants};
+    my $pc = Pod::Coverage->new( package => $name , private => [ qr/^_/ ] );
+    if ( defined $pc->coverage ) {
+        my @uncovered = $pc->uncovered;
+        if ( @uncovered == 1 and $uncovered[0] eq 'LC_MESSAGES' ) {
+            next;
+        }
+
+        is( $pc->coverage, 1.0, $name );
+        if ( $pc->coverage < 1.0 ) {
+            foreach my $name ( @uncovered ) {
+                diag "Function '$name' not documented";
+            }
+        }
+    }
+    else {
+        diag $pc->why_unrated . ' for ' . $name;
+    }
+}
+
+done_testing;