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/requirements/ExistingZCFeaturesGUI.md

@@ -0,0 +1,40 @@
+Existing ZC GUI Features
+========================
+
+ZoneCheck GUI Features which could be included in "Zonemaster"
+
+Link to example : http://www.zonecheck.fr/demo/
+
+Language:
+---------
+
+1. Multiple language support (French and English) is available based on the
+browser language settings of the user
+2. Easy to add more languages other than English and French 
+3. Configuration settings available to select the language of the result of
+the test other than that of the default page 
+
+Usability:
+---------- 
+
+1. Possible to test only with domain name as input 
+2. Possible to test undelegated domains
+3. Possible to select the output format (html/text) of the test report
+4. Possible to test with different test profiles
+5. Has a progress bar which allows the client to have an idea that the tests
+are being conducted even if there is a delay
+6. Possible to select the type of the report generated
+7. Possible to stop the tests on the event of a fatal error
+8. Possible to have a detailed report which shows the test done, condition
+for passing the test and the results of the test with details from the zone
+that is being tested
+9. Possible to limit testing the zone based on the needs of the user (such
+as IPv4 only, TCP only etc..)
+10. Provides a brief description of the test when it is performed
+
+
+Functionality:
+---------------
+1. Possible to add new output formats easily
+2. Possible to include different profile tests easily
+3. Possible to add extra test easily