Simplify port mapping: expose 3500 externally, use 3000 internally

- Map host port 3500 to container port 3000
- Keep Next.js on default port 3000 inside container
- Simplifies auth configuration

docker-compose.yml

@@ -4,12 +4,12 @@ services:
       context: .
       dockerfile: Dockerfile
     ports:
-      - "3500:3500"
+      - "3500:3000"
     environment:
       - NODE_ENV=production
       - DATABASE_URL=${DATABASE_URL}
-      - AUTH_URL=${AUTH_URL:-http://localhost:3500}
-      - NEXTAUTH_URL=${NEXTAUTH_URL:-http://localhost:3500}
+      - AUTH_URL=http://localhost:3500
+      - NEXTAUTH_URL=http://localhost:3500
       - NEXTAUTH_SECRET=${NEXTAUTH_SECRET}
       - AUTH_SECRET=${AUTH_SECRET}
       - AUTH_TRUST_HOST=true