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/public/specifications/test-zones/Engine/README.md

@@ -0,0 +1,18 @@
+# Specification of test scenarios for Zonemaster-Engine Perl modules
+
+This document structure contains test scenario specifications for
+Zonemaster-Engine Perl Modules, except for test scenarios for [Test Case]
+implementations and implementation of [MethodsV2], which are found in sibling
+structures.
+
+The test scenarios found here are for various Perl modules. The specifications
+are split by Perl module, and sometimes further split by area.
+
+The following specifications are available:
+
+* [Recursor-PM](Recursor-PM/README.md)
+
+
+[Test Case]:                                       ../../tests/README.md 
+[MethodsV2]:                                       ../../tests/MethodsV2.md 
+