Fix nginx port: bind to 3000 instead of 80 for NPM compatibility

NPM proxies beachpartyballoons.com → host:3000. Binding to 80 conflicts
with NPM which owns that port.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

docker-compose.yml

@@ -5,7 +5,7 @@ services:
     image: nginx:alpine
     container_name: bpb-nginx
     ports:
-      - "80:80"
+      - "3000:80"
     volumes:
       - ./nginx/nginx.conf:/etc/nginx/nginx.conf:ro
       - ./nginx/well-known:/etc/nginx/well-known:ro