I need to add user authentication to my AI tool. Requirements:

1. Signup page with email and password
2. Login page with email and password
3. Only authenticated users can access the main AI tool
4. Redirect unauthenticated users to signup page
5. Simple user profile created automatically after signup
6. Clean, simple design that matches my existing tool

Please set up basic authentication with Supabase. 

We'll be adding payment processing later. For now focus on the above.