Add core identity flow with persisted sessions and updated platform docs

[rgomids]

Summary

• add the Phase 1 core identity flow with account creation, email/password login, JWT issuance, and session invalidation
• introduce persisted users, accounts, credentials, and sessions with supporting SQL migrations and explicit PostgreSQL repositories
• wire identity into bootstrap, configuration, error handling, and module composition
• update README, architecture, commands, handoff, phase status, and changelog to reflect the new identity foundation
• expand unit, integration, and functional coverage for identity and bootstrap behavior

Testing

• npm run build
• npm run test:unit
• npm run test:integration
• npm run test:functional