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/public/specifications/tests/Zone-TP/zone07.md

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+## ZONE07: SOA master is not an alias
+
+### Test case identifier
+**ZONE07** SOA master is not an alias
+
+### Objective
+
+Any NS type record should not be a CNAME. The SOA MNAME should in this
+respect not be a CNAME.
+
+Quote from 2.4 in [RFC 1912](https://datatracker.ietf.org/doc/html/rfc1912):
+
+> Having NS records pointing to a CNAME is bad and may conflict badly
+> with current BIND servers.
+
+The SOA MNAME field is described in section 3.3.13 in
+[RFC 1035](https://datatracker.ietf.org/doc/html/rfc1035).
+
+The [RIPE-203](https://www.ripe.net/publications/docs/ripe-203) recommendation
+for the minimum value 2 days, but the negative caching is now the norm.
+DNSCheck has a recommended value of between 300 seconds (5 minutes) and
+86400 seconds (1 day).
+
+### Inputs
+
+The domain name to be tested.
+
+### Ordered description of steps to be taken to execute the test case
+
+1. Retrieve the SOA record from a delegated name server for the domain.
+2. If the answer from step 1 is not authoritative, iterate step 1 until there is an authoritative answer.
+3. Retrieve the SOA MNAME value from the SOA record.
+4. Query for A and AAAA records for the host from MNAME.
+5. If the answer to the query is a CNAME, this test case fails.
+
+### Outcome(s)
+
+If the SOA MNAME field is pointing to a CNAME, this test case fails.
+
+### Special procedural requirements
+
+None.
+
+### Intercase dependencies
+
+None.