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/docs/files-description.md

@@ -0,0 +1,48 @@
+# Files Description
+
+./lib/Zonemaster/Backend/RPCAPI.pm
+    The main module
+
+./script/zonemaster_backend_rpcapi.psgi
+    The Plack/PSGI module. The main entry module for a Plack/PSGI server (like Starman)
+
+./lib/Zonemaster/Backend/Config.pm
+    The Configuration file abstraction layer
+
+./share/backend_config.ini
+    A sample configuration file
+
+./CodeSnippets/Client.pm
+./CodeSnippets/client.pl
+    A sample script and library to communicate with the backend.
+
+./lib/Zonemaster/Backend/DB.pm
+    The Database abstraction layer.
+
+./lib/Zonemaster/Backend/DB/MySQL.pm
+    The Database abstraction layer MySQL sample backend.
+
+./lib/Zonemaster/Backend/DB/SQLite.pm
+    The Database abstraction layer SQLite sample backend.
+
+./lib/Zonemaster/Backend/DB/PostgreSQL.pm
+    The Database abstraction layer PostgreSQL backend.
+
+./lib/Zonemaster/Backend/Translator.pm
+    The translation module.
+
+./lib/Zonemaster/Backend/TestAgent.pm
+    The TestAgent main module.
+
+./script/execute_zonemaster_P10.pl
+./script/execute_zonemaster_P5.pl
+    The scripts to execute tests with differents priorities (application level priorities).
+
+./script/execute_tests.pl
+    The main Test Agent entry point to execute from crontab.
+
+./t/test01.t
+./t/test_mysql_backend.pl
+./t/test_postgresql_backend.pl
+./t/test_validate_syntax.t
+    Test files.