0fc6c68a99
Issue persistent signed anonymous IDs and accept cookie/token-bound events. Resolve verified email, phone, OAuth, and namespaced third-party IDs into transactionally merged master identities with historical event aliases. Protect shared-device account switching, tenant isolation, and event retries. Store sparse canonical profiles as PostgreSQL JSONB or local SQLite JSON. Support an optional versioned Cassandra wide-column projection through a transactional outbox, retry worker, and immediate canonical read fallback. Document deployment settings and provide opt-in database integration tests. Validation: 43 local tests passed; 6 external database tests skipped. Ruff checks, formatting, and offline uv lock verification passed.