9rth27/PennyWise ? reverse-engineered prompt

Build me a clean Next.js app called PennyWise with Google sign in and sign up through Supabase.

I want the app to feel simple and polished, with a nice landing page, a login flow, and a protected area that only signed in users can see. Please make the auth callback work correctly for both local development and deployment, since I’ve had redirect issues before. Use the app URL from an environment variable, and make sure the Supabase redirect settings line up with it.

Keep the UI modern and mobile friendly, and use the existing components and styles in the project where it makes sense. If anything about the latest Supabase or Next.js auth setup is unclear, look up the current docs online and follow the recommended approach.

Also set things up so the app is easy to run locally, with sensible env examples and clear behavior when a user is not logged in versus when they are logged in.