In the PostgREST docs schema isolation is explained in detail: https://docs.postgrest.org/en/v12/explanations/schema_isolat...
By default, Supabase exposes the public schema directly. This means tables created in the standard public schema are immediately accessible as API endpoints.
The truth is there's just no way around learning about the underlying technology or building up the necessary experience if one wants to create robust and secure software and products. No amount of AI will solve it, sorry, it's a harsh truth.