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/utils/app.utils.ts

@@ -0,0 +1,92 @@
+import  { expect, type Page } from "@playwright/test";
+import { findMockResponse } from "../interceptors/mock.interceptor";
+
+export function goToHome(page: Page) {
+  return page.goto('/');
+}
+
+export async function mounted(page: Page) {
+    await expect(page.locator('body')).toHaveAttribute('data-domain-test-hydrated', 'true');
+}
+
+export async function setupApiMocks(page: Page) {
+  // Match any URL ending with /api
+  await page.route(/\/api$/, async (route) => {
+    const request = route.request();
+    const method = request.method();
+    const url = request.url();
+
+    let body;
+    try {
+      body = request.postDataJSON();
+    } catch (e) {
+      body = null;
+    }
+
+    const mockResponse = findMockResponse(url, method, body);
+
+    if (mockResponse) {
+      await route.fulfill({
+        status: 200,
+        contentType: 'application/json',
+        body: JSON.stringify(mockResponse),
+      });
+    } else {
+      console.log('⚠️  No mock found for request:', { method: body?.method, params: body?.params });
+      // If no mock is found, continue with the actual request
+      await route.continue();
+    }
+  });
+}
+
+export function setLang(page: Page, lang: string) {
+  return Promise.all([
+    page.waitForSelector('select#languageSwitcher'),
+    page.locator('select#languageSwitcher').selectOption(lang),
+  ]);
+}
+
+export async function closeOptions(page: Page) {
+    const toggle = page.locator('#advanced-toggle');
+    const panel = page.locator('#advanced-options');
+
+    // Ensure the toggle is visible/ready
+    await expect(toggle).toBeVisible();
+
+    // If it's currently open, close it
+    if (await toggle.getAttribute('aria-expanded') === 'true') {
+        await toggle.click();
+    }
+
+    // Confirm it's actually closed
+    await expect(toggle).toHaveAttribute('aria-expanded', 'false');
+
+    // Wait for the panel to be hidden / detached
+    await panel.waitFor({ state: 'hidden' });
+}
+
+export async function showOptions(page: Page) {
+    const toggle = page.locator('#advanced-toggle');
+
+    // Wait for toggle to be ready
+    await expect(toggle).toBeVisible();
+
+    // Click if not already open
+    if (await toggle.getAttribute('aria-expanded') !== 'true') {
+        await toggle.click();
+    }
+
+    // Ensure it's REALLY open
+    await expect(toggle).toHaveAttribute('aria-expanded', 'true');
+
+    // Wait for the content you're about to use
+    await page.locator('#advanced-options').waitFor({ state: 'visible' });
+}
+
+export function clearBrowserCache(page: Page) {
+  return Promise.all([
+    page.evaluate(() => window.localStorage.clear()),
+    page.evaluate(() => window.sessionStorage.clear()),
+    page.context().clearCookies(),
+  ])
+}