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/README-Bind.md

@@ -0,0 +1,31 @@
+# Bind
+
+## Generate DNS records
+
+Bind is used for some test cases to generate some DNS records, specifically
+DNSSEC, NSEC3 and RRSIG records. That is done when the those must validate,
+e.g. for DNSSEC10 test scenarios. To create those DNS records Bind must be
+started.
+
+
+## Running Bind
+
+Bind is never used to serve the test zones. That is done by CoreDNS, and in the
+future IBDNS. 
+
+
+## Configuring Bind
+
+Specific IP addresses must be reserved for Bind in `address-plan.md`. Under the
+directory named after the test case a `Bind` directory is created, e.g.
+`DNSSEC-TP/dnssec10/Bind/`. In that a`named.conf` is created, i.e. one
+`named.conf` for each test case that need Bind. In `named.conf` it must be
+specified which IP addresses that Bind should be listening on.
+
+Use an existing `named.conf` as a template.
+
+
+## Starting, stopping reloading Bind
+
+See the `Bind` directory for the specific test case.
+