Sign-ups through the Better Auth proxy write to auth_users, but the
bootstrap gate counted users — which only mirrors on the first
authenticated call. In that window a second public registration was
accepted on both the proxied sign-up and the native register endpoint.
countLocalUsers now unions users with auth_users (guarded by
to_regclass so backend-only installs still work), and handleRegister
uses it instead of its own inline count.
e2e-verified on a live stack: users=0/auth_users=1 already reports
mode=login and 403s both public paths; internal-token bypass works,
wrong token refused, authed POST /users creates users (201), and the
users mirror still populates on first authenticated call.
Generated with [Devin](https://devin.ai)
Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>