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/FR09.e2e-spec.ts

@@ -0,0 +1,17 @@
+import {test, expect} from './global-setup';
+
+import {goToHome, setLang} from './utils/app.utils';
+
+test.describe('Zonemaster test FR09 - [Once a language is chosen, all other links should open in that respective language]', () => {
+    test.beforeEach(async ({page}) => {
+        await goToHome(page);
+        await setLang(page, 'fr');
+    });
+
+    test('should keep french when opening faq page', async ({page}) => {
+        await expect(page.locator('input[name="domain"]')).toHaveAttribute('placeholder', 'Nom de domaine');
+        await page.goto('/fr/faq/');
+        await expect(page.locator('main h1')).toHaveText('Questions fréquentes');
+        await expect(page.locator('a.zm-menu__item[href$="/fr/"]')).toHaveText("Démarrer un test");
+    });
+});