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-gui/demo/demo.ts

@@ -0,0 +1,24 @@
+import '../src/themes/default/styles/theme.css';
+import '../src/themes/default/styles/foundation.css';
+import '../src/assets/fonts/bootstrap-icons.min.css';
+import '../src/lib/styles/style.css';
+import { createTestAgent } from '../src/lib/main.ts';
+
+const agent = createTestAgent();
+const button = document.getElementById('headless') as HTMLButtonElement;
+
+agent.subscribe((state, context) => {
+    if (state === 'testing') {
+        button.disabled = true;
+        button.innerText = `Testing...${context.progress}%`;
+    } else {
+        button.disabled = false;
+        button.innerText = 'Start test';
+    }
+});
+
+button?.addEventListener('click', () => {
+    agent.transition('START', {
+        domain: 'zonemaster.net',
+    });
+});