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>

Dockerfile.gui

@@ -0,0 +1,23 @@
+# ── Stage 1: Build Astro static site ─────────────────────────────────────────
+FROM node:22-alpine AS builder
+
+WORKDIR /app
+
+COPY zonemaster-gui/package*.json ./
+RUN npm ci
+
+COPY zonemaster-gui/ ./
+
+# Build as static production site with Spanish as default, API proxied via /api
+ENV NODE_ENV=production
+ENV PUBLIC_API_URL=/api
+ENV PUBLIC_BASE_URL=/
+RUN npm run build
+
+# ── Stage 2: Serve with nginx ─────────────────────────────────────────────────
+FROM nginx:alpine
+
+COPY --from=builder /app/public/dist /usr/share/nginx/html
+COPY nginx.conf /etc/nginx/conf.d/default.conf
+
+EXPOSE 80