FastAPI app with invite-code signup, message send/relay over
WebSocket, and the DB schema from roadmap.md Phase 1 §2.1 (users,
contacts, conversations, messages, twin_settings, whitelist_rules,
escalation_logs). Defaults to SQLite for local dev, PostgreSQL in
prod per tech-design.md §8.
Verified end-to-end with TestClient: signup, duplicate-invite-code
rejection (409), message persistence, 404 on an unknown conversation,
and WebSocket broadcast delivery all behave as expected.
Push notifications and the AI pipeline integration (item 3) are not
in this commit -- see backend/README.md and roadmap.md's checklist.
Claude