Squash Cloud schema to one fresh Postgres baseline #995

Parent

Spec: 1.0 tree cleanup and release contracts

What to build

Replace pre-stable migration history with one fresh baseline that represents the cleaned Cloud schema, and use the existing Effect Postgres harness in place of the promise-based one.

Acceptance criteria

• baseline.postgres.test passes against an empty database with the final schema.
• The duplicate promise-based Postgres harness and obsolete migrations are gone; existing Postgres-backed tests use the Effect harness.

Blocked by

• Remove retired Cloud authoring and capability paths
• Prune retired Cloud pages and server functions
• Make Cloud config and billing optional for self-hosters