Fix Dockerfile to copy all files and build Next.js app

- Change COPY * to COPY . to include subdirectories (public/, app/, etc.)
- Add npm run build step for Next.js production build
- Change CMD from node server.js to npm start for Next.js

frontend/Dockerfile

@@ -1,7 +1,8 @@
 FROM node
 WORKDIR /app
-COPY * /app/
+COPY . /app/
 RUN npm i
+RUN npm run build
 RUN chmod +x /app/entrypoint.sh
 ENTRYPOINT ["/app/entrypoint.sh"]
-CMD ["node", "server.js"]
+CMD ["npm", "start"]