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-backend/share/backend_config.ini

@@ -0,0 +1,50 @@
+# For documentation of the backend_config.ini file see
+# https://github.com/zonemaster/zonemaster/blob/master/docs/public/configuration/backend.md
+
+[DB]
+engine            = SQLite
+polling_interval  = 0.5
+
+[MYSQL]
+host     = localhost
+user     = zonemaster
+password = zonemaster
+database = zonemaster
+
+[POSTGRESQL]
+host     = localhost
+user     = zonemaster
+password = zonemaster
+database = zonemaster
+
+[SQLITE]
+database_file = /var/lib/zonemaster/db.sqlite
+
+[ZONEMASTER]
+#max_zonemaster_execution_time            = 600
+#number_of_processes_for_frontend_testing = 20
+#number_of_processes_for_batch_testing    = 20
+#lock_on_queue                            = 0
+#age_reuse_previous_test                  = 600
+
+[RPCAPI]
+
+# Uncomment to enable API method "add_api_user"
+#enable_add_api_user = yes
+# Uncomment to disable API method "add_batch_job"
+#enable_add_batch_job = no
+
+[LANGUAGE]
+locale = da_DK en_US es_ES fi_FI fr_FR nb_NO sl_SI sv_SE
+
+[PUBLIC PROFILES]
+#example_profile_1=/example/directory/test1_profile.json
+#default=/example/directory/default_profile.json
+
+[PRIVATE PROFILES]
+#example_profile_2=/example/directory/test2_profile.json
+
+[METRICS]
+# Uncoment the following option to enable the metrics feature
+#statsd_host = localhost
+#statsd_port = 8125