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/test-zone-data/start-coredns.sh

@@ -0,0 +1,55 @@
+#!/bin/bash
+
+set -u
+
+usage() { (echo "Usage: sudo $0" 1>&2;
+           echo
+           echo "Start CoreDNS for Zonemaster test zone environment" 
+           echo )1>&2;
+          exit 1;
+        }
+
+while getopts "h" o; do
+    case "${o}" in
+        h)
+            usage
+            ;;
+        *)
+            usage
+            ;;
+    esac
+done
+shift $((OPTIND-1))
+
+# Make sure the script is run by  root
+if [ $(id -u) -ne 0 ] ; then
+    echo "You must be root." 1>&2
+    echo "Run 'sudo $0'" 1>&2
+    exit 1
+fi
+
+# Get path to this script
+path=$(dirname $0)
+
+# Go to the directory of the script
+cd $path || exit 1
+
+# main.cfg must be in the same folder as this script
+maincfg="main.cfg"
+
+# Is CoreDNS already running? One instance at a time.
+if ps --no-headers -fC coredns | grep coredns ; then
+    echo "Only one instance of CoreDNS must be run at a time."
+    echo "Kill old instances or break with CTRL-C."
+    echo
+    killall -s 9 -i coredns
+    sleep 2
+fi
+
+if ps --no-headers -fC coredns | grep coredns ; then
+    echo "Cannot start CoreDNS since it is already running. Exit."
+else
+    coredns --conf ${maincfg}
+fi
+
+