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/test-zone-data/DNSSEC-TP/dnssec07/README.md

@@ -0,0 +1,13 @@
+[This directory](.), i.e. the same directory as this README file, holds zone
+files and configuration files to implement the test zones for the scenarios
+defined in [DNSSEC07 test scenario specification].
+
+For these test zones the following files are found in [This directory](.):
+* Zone files for `dnssec07.xa` and other related zones.
+* CoreDNS configuration file
+* Zone file and hint file for local root zone.
+* Output from `zonemaster-cli` on all test scenarios in
+  [test-zones-output.md](test-zones-output.md).
+
+[DNSSEC07 test scenario specification]:     ../../../docs/public/specifications/test-zones/DNSSEC-TP/dnssec07.md
+