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/playwright.config.ts

@@ -0,0 +1,30 @@
+import { type PlaywrightTestConfig, devices } from '@playwright/test';
+
+const config: PlaywrightTestConfig = {
+    workers: 4,
+    testDir: 'e2e',
+    testMatch: 'e2e/*.e2e-spec.ts',
+    webServer: {
+        command: 'NODE_ENV=testing npm run build && NODE_ENV=testing npm run preview',
+        url: 'http://localhost:4321/',
+        timeout: 120 * 1000,
+        reuseExistingServer: !process.env.CI
+    },
+    expect: {
+        toMatchSnapshot: {
+            maxDiffPixelRatio: 0.01
+        }
+    },
+    use: {
+        headless: true,
+        baseURL: 'http://localhost:4321',
+        viewport: { width: 1920, height: 1080 }
+    },
+    projects: [
+        {
+            name: 'chromium',
+            ...devices['Desktop Chrome']
+        },
+    ],
+};
+export default config;