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.t

@@ -0,0 +1,14 @@
+#!perl -T
+use 5.006;
+use strict;
+use warnings FATAL => 'all';
+use Test::More;
+
+# Ensure a recent version of Test::Pod
+my $min_tp = 1.22;
+eval "use Test::Pod $min_tp";
+plan skip_all => "Test::Pod $min_tp required for testing POD" if $@;
+
+all_pod_files_ok();
+
+done_testing;