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/README-for-doc.zonemaster.net.md

@@ -0,0 +1,53 @@
+<!-- This document replaces public/README.md on doc.zonemaster.net  -->
+
+# Public documentation
+
+# ![Zonemaster][Zonemaster-logo]
+
+<!-- The text below has been taken from the Introduction section in main README and
+should be kept in sync with the source. -->
+
+Zonemaster is a software package that validates the quality of a DNS delegation.
+The ambition of the Zonemaster project is to develop and maintain an open source
+DNS validation tool, offering improved performance over existing tools and providing
+extensive documentation which could be re-used by similar projects in the future.
+
+Zonemaster consists of several modules or components. The components will help
+different types of users to check domain servers for configuration errors and
+generate a report that will assist in fixing the errors.
+
+Zonemaster consists of several modules or components. The components will help
+different types of users to check domain servers for configuration errors and
+generate a report that will assist in fixing the errors.
+
+Zonemaster is developed by [Afnic] and [The Swedish Internet Foundation].
+
+A public instance is running on [zonemaster.net].
+
+<!-- The text below has been copied from public/README.md and should be kept in
+sync with the source -->
+
+The public documentation is divided into the following main categories:
+
+* [Release information](RELEASE.md) gives release information of latest release.
+* [Installation](installation/README.md) contains documents that explain how to
+  install the different components of Zonemaster.
+* [Upgrading](upgrading/README.md) contains documents that explain how to upgrade
+  a Zonemaster installation.
+* [Configuration](configuration/README.md) contains documents that explain how a
+  Zonemaster installation can be configured.
+* [Using](using/README.md) contains user guides to the different components of
+  Zonemaster.
+* [Specifications](specifications/README.md) contains specifications of the
+  Zonemaster test cases, test types and test zones.
+* [Development](development/README.md) contains information for developers both
+  in and outside the Zonemaster project.
+* [License](LICENSE.md) gives the license information for Zonemaster.
+
+
+[AFNIC]:                                            https://www.afnic.fr/en/
+[The Swedish Internet Foundation]:                  https://internetstiftelsen.se/en/
+[Zonemaster.net]:                                   https://zonemaster.net
+
+<!-- Location on doc.zonemaster.net: -->
+[Zonemaster-logo]:                                  ../zonemaster_logo_2021_color.png