add supabase auth (default remains no auth)

[somethingwentwell]

This pull request introduces the capability to enable Supabase authentication in our application. By leveraging Supabase auth, we can now support both traditional email & password authentication as well as various social login methods.

Changes:
Added environment variables to configure Supabase auth:

• NEXT_PUBLIC_ENABLE_SUPABASE_AUTH: Set to false by default, meaning no authentication is required. If set to true, Supabase auth will be enabled.
• NEXT_PUBLIC_SUPABASE_URL: Configuration for the Supabase URL, defaulted to http://localhost:8000 for development purposes.
• NEXT_PUBLIC_SUPABASE_ANON_KEY: The anonymous key necessary for Supabase operations, to be replaced with the actual key in production.

Implementation:
The implementation checks the NEXT_PUBLIC_ENABLE_SUPABASE_AUTH variable. If it's true, the application initializes Supabase client with the provided URL and anonymous key, thus enabling the email & password and social logins supported by Supabase.