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/Address-TP/address03.md

@@ -0,0 +1,63 @@
+## ADDRESS03: Reverse DNS entry matches name server name
+
+### Test case identifier
+**ADDRESS03** Reverse DNS entry matches name server name
+
+### Objective
+
+Some anti-spam techniques use reverse DNS lookup to allow incoming traffic.
+In order to prevent name servers to be blocked or blacklisted, DNS 
+administrators should publish PTR records associated with the name server
+addresses. 
+
+Moreover, as mentioned in paragraph 2.1 of [RFC
+1912](https://datatracker.ietf.org/doc/html/rfc1912) when a PTR record exists, it must match the host
+name.
+
+### Inputs
+
+The domain name to be tested.
+
+### Ordered description of steps to be taken to execute the test case
+
+1. Obtain the IP addresses of each name server of the domain from the child
+   using [Method5](../Methods.md).
+   These IP addresses can be associated to the name servers through a hash 
+   table where each address is a key and the name server it's unique value.
+   Let's call this hash table HASH1.
+
+2. Obtain the reverse DNS entries associated to name servers names as described
+   in test case [ADDRESS02](address02.md). Let's call its outcome HASH2 which
+   consists of IP addresses as keys and hostnames as values. As multiple PTR
+   records are allowed, an IP address can have several corresponding hostnames.
+
+3. Compare HASH2 to HASH1. 
+
+   Parse the address list of HASH1. 
+
+   For an address (a) of HASH1, take the corresponding hostname (h) in HASH1. 
+   If this hostname (h) is present in the hostnames list associated to this
+   address (a) in HASH2, then the test succeeds for address (a).
+
+   If the hostname (h) does not match any hostnames associated to address (a)
+   in HASH2, then the test fails for address (a).
+
+   If the test fails for one IP address, the whole test case fails.   
+   
+
+### Outcome(s)
+
+Multiple addresses and multiple PTR records are allowed. The test 
+succeeds if every name server address has one or more PTR records
+and one of these records matches the server name.
+If one address doesn't match, the whole test case fails.
+
+### Special procedural requirements
+
+None.
+
+### Intercase dependencies
+
+Some of the input of this test comes as the result of test case
+[ADDRESS02](address02.md). [ADDRESS02](address02.md) must succeed
+prior to proceed with this test case [ADDRESS03](address03.md).