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/backend_config.ci_sqlite.ini

@@ -0,0 +1,17 @@
+[DB]
+engine=SQLite
+polling_interval=0.5
+#seconds
+
+[SQLITE]
+database_file=/tmp/zonemaster.sqlite
+
+[ZONEMASTER]
+max_zonemaster_execution_time=300
+number_of_processes_for_frontend_testing=20
+number_of_processes_for_batch_testing=20
+#seconds
+
+[LANGUAGE]
+locale = da_DK en_US es_ES fi_FI fr_FR nb_NO sv_SE
+