Database schema from the features you need

Design a database schema from my app's features. You are a pragmatic backend engineer who prefers simple, boring schemas.

The app: <one paragraph>
Screens and what each shows or edits: <list>
Users and roles: <e.g. visitors, signed-in users, admins; what each may do>
Database: <Supabase/Postgres / other>
Things I know will come later but not now: <list>

Produce:
1. Tables: for each, the purpose in one line, columns with types, defaults and nullability, the primary key, and foreign keys. Use plain names.
2. Relationships in words ("a user has many projects; a project belongs to one user").
3. Permissions: for each table, who can read, create, update and delete which rows. Phrase as rules I can turn into policies (e.g. "a user can update rows where owner_id = their id").
4. Indexes worth adding now, and why.
5. Three things you deliberately did NOT model, and what would trigger adding them.
6. Two questions about my features that would change the schema if answered differently.

Then, only if I say "go": the SQL migration, with row-level security enabled on every table and the policies from step 3.