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/.github/pull_request_template.md

@@ -0,0 +1,15 @@
+## Purpose
+
+This PR...
+
+## Context
+
+(e.g. Fixes #9999, Follow-up to #9999, etc.)
+
+## Changes
+
+...
+
+## How to test this PR
+
+...

zonemaster-gui/.github/workflows/ci.yml

@@ -0,0 +1,36 @@
+name: CI
+
+on:
+  push:
+    branches:
+      - develop
+      - master
+      - 'releases/**'
+  pull_request:
+    branches:
+      - develop
+      - master
+      - 'releases/**'
+jobs:
+  tests_e2e:
+    name: Run end-to-end tests
+    runs-on: ubuntu-22.04
+    steps:
+      - uses: actions/checkout@v3
+
+      - uses: actions/setup-node@v3
+        with:
+          node-version: 24.x
+          cache: npm
+
+      - name: Install dependencies
+        run: npm install
+
+      - name: Install e2e dependencies
+        run: npm run e2e:install-deps
+
+      - name: Run e2e browsers
+        run: npm run e2e:install
+
+      - name: Run e2e tests
+        run: npm run e2e