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/maintenance/ReleaseProcess.md

@@ -0,0 +1,36 @@
+Release process
+===============
+
+This process has been split into different parts which are described in their
+own documents.
+
+## 1. [Preparation]
+
+The steps in this subprocess should be processed early in the release
+process, definitely before acceptance testing starts, but also before
+development has been completed.
+
+
+## 2. [Test planning]
+
+This phase should be performed after the end of development but before
+acceptance testing starts.
+
+
+## 3. [Create test distributions]
+
+The purpose of this part is to create the test distributions that can be
+used in QA testing for a release. It can also be used to create test
+distributions to verify a pull request.
+
+
+## 4. [Release]
+
+The steps in this part executes the actual release. They assume that
+development, the preparation steps and the QA testing have been concluded.
+
+
+[Create test distributions]: ReleaseProcess-create-test-distribution.md
+[Preparation]:               ReleaseProcess-preparation.md
+[Release]:                   ReleaseProcess-release.md
+[Test planning]:             ReleaseProcess-test-planning.md