- Create timeline.unified_audit_events table with SHA-256 hash chain - Create timeline.unified_audit_sequences for per-tenant tracking - Replace IngestAuditEventStore (in-memory) with PostgresUnifiedAuditEventStore - Preserve chain integrity via serializable isolation - Mark AUDIT-001 as DONE in sprint tracker Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>