Add a single getUserDisplayName(user) function to app/models/user.ts that
encapsulates the username → displayName fallback logic. Replace 9 scattered
inline expressions across the codebase (owner-map, scoring-calculator,
league routes, settings, invite flow, draft API, Clerk webhook) with calls
to the shared helper.
No behaviour change — all existing logic preserved, just centralised.
https://claude.ai/code/session_01VAkeDDVZMYS1DweQnUrRnH
