Says your context is null, find useContext line in your app and check

This isn't helpful at all, because the error very likely is throwing in Next-internal code. It's a completely different reason such as forgetting to default export layouts or pages which causes Next to trip up.

How can I solve the problem

such as forgetting to default export layouts or pages which causes Next to trip up.

Check that you didn't forget something that could this

first run app in dev mode, not build. with npm run dev

you mean run npm run build && npm run start? (which they are already doing)

no we need to see dev logs, we dont need things in .next

im pretty sure the builder has better errors... but we can see ig