Pydantic v2 + FastAPI serializes Field(alias="_id") as _id in JSON,
so client.id was always undefined on the frontend — causing option
values to fall back to text content ("3M") and firing /clients/3M/teams 404s.
- Remove Field(alias="_id") from Client/Team/Project models; id is now a
plain string field populated explicitly in _client_from_doc etc.
- API now returns id not _id, matching the TypeScript Client interface
- Add clientId !== "undefined" guard to useTeams, usePMs, useProjects
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>