`npx next-video init` doesn't work with monorepos

[decepulis]

Tried running in my turborepo, against app/web/package.json. Since the script checks for a lockfile and the lockfile is at root, the script fails to run.

[heff]

Fun with wizards! 🧙 @mmcc loves me right now.

If this is a tough or brittle fix, we could just add a "are you using a monorepo" question to the prompts and point them to the manual setup docs.