Key point
Production means real URL
Your project is not ready when it works on localhost. It is ready when a judge can open a public URL on a phone and use the main flow.
For this track, keep your App Router features working: layouts, Server Components, server fetches, and route handlers.
Build before deploy
A production build catches problems that dev mode may hide. Run it before every deployment, especially after adding a route handler or server-side data fetch.
Next.js production scripts should include dev, build, and start. The build step prepares the app. The start step runs the production server locally.