apps/api/src/auth/linkOidc.ts (new):
- OidcLinkConflictError: thrown when iss+sub already belongs to a different user
- linkOidcToUser(userId, iss, sub): preflight SELECT for conflict, then db.transaction
(UPDATE users SET oidc_iss/sub/claimed + DELETE local_credentials); atomic, no email (D-10)
- 88 lines; no email in source (D-10/T-19-08 assertion passes)
apps/api/src/routes/me.ts:
- POST /api/me/link-oidc: resolveUserId (401 if null), sign state JWT
({ linkUserId, nonce, iat, exp } HS256 with LOCAL_SESSION_SECRET, 10-min window)
- Returns { signedState, authorizationUrl } — 19-03 /callback reads linkUserId from state
- authorizationUrl constructed from OIDC env vars when configured, null otherwise
- T-19-09: per-request nonce in state prevents CSRF/replay