BetterAuth rejects cross-origin requests unless the origin is in
trustedOrigins. The web dashboard at localhost:3000 was getting
"Invalid origin" errors when calling auth endpoints on localhost:4000.
Reads GATEWAY_CORS_ORIGIN env var (comma-separated), defaults to
http://localhost:3000.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
