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/DNSCheck-Batch-Requirements.txt

@@ -0,0 +1,23 @@
+Requirements for batch functionality (taken from DNSCheck 1.*'s) for the Zonemaster project. This is the functional requirements from the current DNSCheck.
+
+Today we have several users of batch functionality, for example:
+1. The Web interface uses the batch functionality to queue tests and to display history of test results. 
+2. The automatic support emails going out to IIS's Registrars to test and track domains as they change.
+3. To generate DNS delegation quality statistics.
+
+A batch function could be called a user of the Zonemaster test framework with the ultimate goal of easily accessing stored test results in an efficient way for statistics or reporting purposes.
+One type of batch user: https://github.com/dotse/dnscheck/tree/master/webui
+Another type of batch user: https://github.com/dotse/dnscheck/blob/master/engine/apps/dnscheck-dispatcher
+
+Functions:
+[1.1] A batch function MUST support grouping of test results, thus traceable and unique flagged runs for as few as one but as many as millions of zones (Current DNSCheck terminology: SOURCE).
+ [1.2] The batch function MUST make sure that every single test result has a unique identifier, and the result must be retrievable using the unique identifier, timestamp or test domain (Current DNSCheck terminology: UNIQUE_ID).
+ [1.3] A batch function MUST be able to keep complete history per test run that is linked to what source generated the test as per [1.1] (Current DNSCheck terminology: HISTORY).
+ [1.4] A batch function MUST be able to prioritize test runs based on an extendable (0..n) priority number (not "high/low" or similar) (Current DNSCheck terminology: QUEUE).
+ [1.5] The batch function MUST be able to store complete test results of up to several million tests and make these efficiently retrievable (within seconds) based on the domain as keyword for listing previous test runs.
+ [1.6] The batch function MUST log when a test was started, when it ended, the complete test result, what source generated the result and at what priority (TRACEABILITY).
+ [1.7] The batch function MUST support a queue system, running tests based on the level of priority as per [1.4].
+ [1.9] The batch function MUST support a configurable maximum number of concurrent domain tests it starts and maintains until completed, also based on priority as per [1.4].
+
+[ future IIS special re-delegation test ]
+[1.8] The batch function MUST be able to use information (if available) of previously used name servers for any domain being tested (HISTORY #2).