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/templates/specifications/tests/TestCaseIdentifierSpecification.md

@@ -0,0 +1,36 @@
+# Test Case Identifier Specification
+
+All test cases belong to one specific test level and their names are based on
+that test level’s name. The following test levels are defined and available:
+
+* Address
+* Basic
+* Connectivity
+* Consistency
+* DNSSEC
+* Delegation
+* Nameserver
+* Syntax
+* Zone
+
+The test level name is not case-sensitive, but the forms defined above
+must be used when referring to the test levels, i.e. only the first letter
+uppercase, expect for acronyms for which all uppercase is used.
+For example "Address" and neither "ADDRESS" nor "address".
+
+The test case identifier in the test case specification (both in the main
+headline and in the "Test case identifier" section) uses the test level name,
+as defined above, and has the format: `{Test level name} + {Index}`
+
+When referencing to a test case, for readability, the letter case defined
+above must be used for the test level name.
+
+The `{Index}` is a two-digit suffix 01-99, and should be selected so that the
+test case identifier is unique. Normally the first free index is selected.
+
+Example of test case identifiers:
+
+* Address03
+* Basic04
+* DNSSEC15
+* Zone06