feat: add durable enterprise authorization state, approvals, and receipts

[prayingperceptions]

Summary

• add a transactional EnterpriseStore abstraction with PostgreSQL and in-memory implementations
• persist policies, contracts, nonce consumption, revocations, authorization events, approvals, and receipts
• make the production enterprise entrypoint require DATABASE_URL and use PostgreSQL
• add atomic approval decisions/consumption with separation of duties
• bind receipts to persisted authorization events and action digests
• add durable-state red-team regression coverage

Security posture

Production startup uses the Postgres store and tenant-bound JWT authentication. Nonce consumption and approval consumption use database uniqueness/row locks to prevent replay across instances. Receipts cannot be attached to an unknown or mismatched authorization event.

Validation

CI is the authoritative build/test check. The branch contains regression tests for immutable policy versions, nonce replay, revocation, approval separation of duties, one-time approval consumption, and receipt binding.