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-preparation.md

@@ -0,0 +1,107 @@
+Release process - Preparation
+=============================
+
+
+The steps in this document should be processed early in the release
+process, definitely before acceptance testing starts, but also before
+development has been completed.
+
+
+## 1. Update prerequisites
+
+Make sure the [declaration of prerequisites] is up to date with regard to
+[SupportCriteria].
+
+
+## 2. Update [CI] configuration
+
+Make sure the Travis configuration for each repo, in the `develop` branch
+is up to date with the [supported Perl versions].
+
+ * zonemaster-ldns - [.travis.yml][ldns.travis]
+ * zonemaster-engine - [.github/workflows/ci.yml][engine.github-actions]
+ * zonemaster-cli - [.travis.yml][cli.travis]
+ * zonemaster-backend - [.travis.yml][backend.travis]
+
+> Zonemaster-GUI uses no Perl and Zonemaster/Zonemaster uses no Travis.
+
+
+## 3. Verify that META.yml will have all the correct data
+
+> This section is not relevant for Zonemaster-GUI or Zonemaster/Zonemaster.
+
+META.yml is created by Makefile.PL so if META.yml is not correct, then
+Makefile.PL must be updated.
+
+  1. Make a clean clone for each repository
+```
+     git clean -dfx
+     git reset --hard
+```
+  2. Check out the `develop` branch. Check out the right commit
+     of the submodule (LDNS) if Zonemaster-LDNS.
+```
+     git checkout origin/develop
+     git submodule update # Zonemaster-LDNS only
+```
+  3. Run
+```
+     perl Makefile.PL --no-ed25519 # zonemaster-ldns only
+     perl Makefile.PL              # other repositories
+```
+  4. Verify that META.yml contains all the paths in the table in [Appendix META]
+     below and that the value at each path matches the listed requirement.
+
+
+## 4. Verify that MANIFEST and MANIFEST.SKIP are up to date
+
+> This section is not relevant for Zonemaster-GUI or Zonemaster/Zonemaster.
+
+MANIFEST must, directly or indirectly, list all files that should be installed.
+MANIFEST.SKIP must list all file that should not be installed, and what is
+counted are all files available when `make dist` is run.
+
+
+## 5. Check for deprecated features
+
+Check all documentation in all repositories for deprecated features that are
+planned to be removed in the upcoming release.
+
+If anything was found and there is no PR to remove it, then create an issue
+labelled `P-High` that something must be done before the release unless there is
+already an issue.
+
+Removed feature will probably require that the major version is increased
+(breaking change). See "[Versions and Releases]".
+
+
+## Appendix META
+
+Requirements for generated META.yml file.
+
+Property             | Requirement
+---------------------|----------------------------------------------------------------------
+abstract             | component tag line
+author               | current maintainer and original author
+license              | [license string]
+name                 | name of the component
+recommends           | all modules that aren't strictly required but still used if available
+requires             | all required modules
+requires.perl        | minimum perl version
+resources.bugtracker | link to the bug tracker
+resources.license    | link to the license text
+resources.repository | link to the repository
+version              | version number of the new release
+
+
+[CI]:                                      https://github.com/travis-ci/travis-ci
+[declaration of prerequisites]:            ../../public/installation/prerequisites.md
+[license string]:                          https://metacpan.org/pod/CPAN::Meta::Spec#license
+[SupportCriteria]:                         SupportCriteria.md
+[ldns.travis]:                             https://github.com/zonemaster/zonemaster-ldns/blob/develop/.travis.yml
+[engine.github-actions]:                   https://github.com/zonemaster/zonemaster-engine/blob/develop/.github/workflows/ci.yml
+[cli.travis]:                              https://github.com/zonemaster/zonemaster-cli/blob/develop/.travis.yml
+[backend.travis]:                          https://github.com/zonemaster/zonemaster-backend/blob/develop/.travis.yml
+[supported Perl versions]:                 ../../public/installation/prerequisites.md#supported-perl-versions
+[Appendix META]:                           #appendix-meta
+[Versions and Releases]:                   ../design/Versions%20and%20Releases.md