Add Docker deployment for Unraid

- Add Dockerfile.unraid with multi-stage build (builds inside container)
- Add docker-compose.unraid.yml for easy deployment
- Add build-and-push.sh script for building and pushing to Gitea registry
- Update root redirect to /unraid dashboard

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

next.config.js

@@ -21,7 +21,7 @@ module.exports = withBundleAnalyzer({
   redirects: async () => [
     {
       source: '/',
-      destination: '/board',
+      destination: '/unraid',
       permanent: false,
     },
   ],