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-backend/share/zm-testagent.lsb

@@ -0,0 +1,60 @@
+#!/bin/sh
+#
+### BEGIN INIT INFO
+# Provides:          zm-testagent
+# Required-Start:    $network $local_fs
+# Required-Stop:     $network $local_fs
+# Should-Start:      mysql postgresql
+# Should-Stop:       mysql postgresql
+# Default-Start:     2 3 4 5
+# Default-Stop:      0 1 6
+# Short-Description: An asynchronous execution backend for Zonemaster Backend
+# Description:       zm-testagent checks the Zonemaster Backend database for new
+#                    tests, executes them and writes back progress and results.
+### END INIT INFO
+
+BINDIR=${ZM_BACKEND_BINDIR:-/usr/local/bin}
+LOGFILE=${ZM_BACKEND_LOGFILE:-/var/log/zonemaster/zm-testagent.log}
+OUTFILE=${ZM_BACKEND_OUTFILE:-/var/log/zonemaster/zm-testagent.out}
+PIDFILE=${ZM_BACKEND_PIDFILE:-/var/run/zonemaster/zm-testagent.pid}
+USER=${ZM_BACKEND_USER:-zonemaster}
+GROUP=${ZM_BACKEND_GROUP:-zonemaster}
+
+#ZM_BACKEND_TESTAGENT_LOGLEVEL='info'  # Set this variable to override the default log level
+
+testagent_args="--logfile=$LOGFILE --outfile=$OUTFILE --pidfile=$PIDFILE --user=$USER --group=$GROUP"
+if [ -n "$ZM_BACKEND_TESTAGENT_LOGLEVEL" ] ; then
+    testagent_args="$testagent_args --loglevel=$ZM_BACKEND_TESTAGENT_LOGLEVEL"
+fi
+
+start () {
+    $BINDIR/zonemaster_backend_testagent $testagent_args start || exit 1
+}
+
+stop () {
+    $BINDIR/zonemaster_backend_testagent $testagent_args stop
+}
+
+status () {
+    $BINDIR/zonemaster_backend_testagent $testagent_args status
+}
+
+case "$1" in
+    start)
+        start
+        ;;
+    stop)
+        stop
+        ;;
+    restart|force-reload)
+        stop
+        start
+        ;;
+    status)
+        status
+        ;;
+    *)
+        echo "usage: $0 [start|stop|restart|status]"
+        exit 1
+esac
+exit 0