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/e2e/FR03.e2e-spec.ts

@@ -0,0 +1,36 @@
+import { test, expect } from './global-setup';
+
+import { goToHome, setLang, showOptions } from './utils/app.utils';
+
+test.describe('Zonemaster test FR03 - [All appropriate fields should be writable]', () => {
+  test.beforeEach(async ({ page }) => {
+    await goToHome(page);
+    await setLang(page, 'en');
+    await page.waitForLoadState('networkidle');
+  });
+
+  test('should be able to write in the main input', async ({ page }) => {
+    const testString = 'afnic.fr';
+
+    const domainInput = page.locator('#zmDomainTestForm input[name="domain"]').first();
+
+    await domainInput.focus();
+    await page.keyboard.type(testString);
+    await expect(domainInput).toHaveValue(testString);
+
+    await showOptions(page);
+    await page.waitForTimeout(400);
+
+    const nsInput = page.locator('input[name="nameservers[0][ns]"]').first();
+
+    await nsInput.focus();
+    await page.keyboard.type(testString);
+    await expect(nsInput).toHaveValue(testString);
+
+    const keytagInput = page.locator('input[name="ds_info[0][keytag]"]').first();
+
+    await keytagInput.focus();
+    await page.keyboard.type(testString);
+    await expect(keytagInput).toHaveValue(testString);
+  });
+});