Rework the supabase stack so every app owns an isolated Postgres schema
(= program name) instead of sharing `public` with a table_prefix. This
gives a clean, knowable teardown and drops migration version tracking to
per-app, so version tokens can no longer collide across apps.
- stacks: add StackHandler.owns_data + teardown() (default no-op). Supabase
build now creates+grants the app schema, tracks migrations in
<schema>.schema_migrations, and applies each with search_path set to the
schema (write unqualified names). teardown = drop schema <app> cascade.
Fix _substrate_db_url default port 5432 -> 5433 (substrate's direct PG).
- deploy: derive ${supabase_app_schemas} from registered apps; substrate maps
PGRST_DB_SCHEMAS: public,storage,graphql_public${supabase_app_schemas} so
PostgREST exposes each app schema (restart substrate after add/remove).
- delete: generic owns_data -> teardown path behind new --purge-data flag,
replacing the hardcoded supabase remnant note.
- scaffold + docs: new apps born schema-isolated (unqualified tables,
db:{schema}, schema: in supabase.app.yaml).
Paul Payne
b917db5e00