1. Audit log: COALESCE target_username with detail JSON fallback so
deleted users still show their username in the target column
(target_user_id is SET NULL by FK cascade, but detail JSON
preserves the username).
2. Create/get user: add exclude={"active_sessions"} to model_dump()
calls — UserListItem defaults active_sessions=0, so model_dump()
includes it, then the explicit active_sessions=N keyword argument
causes a duplicate keyword TypeError. DB commit already happened,
so the user exists but the response was a 500.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>