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-ldns/CONTRIBUTORS.txt

@@ -0,0 +1,9 @@
+This module is based on the ldns library from NLnet Labs <https://www.nlnetlabs.nl/projects/ldns/>
+
+Contributors to this module:
+Calle Dybedahl <calle@init.se>
+Mattias Päivärinta <mattias.paivarinta@iis.se>
+Wieger Opmeer <opmeer@strato-rz.de>
+Calle Dybedahl <github@cyberpomo.com>
+Jerry Lundström <lundstrom.jerry@gmail.com>
+Patrik Wallström <pawal@blipp.com>