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/Zone-TP/zone11/no-spf-txt.zone11.xa.zone

@@ -0,0 +1,7 @@
+$ORIGIN no-spf-txt.zone11.xa.
+$TTL 3600
+
+$INCLUDE COMMON-SCENARIO-INCLUDE
+
+@               IN  TXT  "There are no SPF policy records here."
+