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/docs/internal/requirements/README.md

@@ -0,0 +1,10 @@
+Requirements (internal)
+=======================
+
+## Purpose of this directory
+
+This contents of this directory includes different files which were used by the
+AFNIC and IIS team internally for the ZM project. Any of the contents of this
+directory will not be useful for any type of users of the Zonemaster software,
+other than the Afnic and IIS team.
+