The booking login step showed only a generic error when /api/auth/token
returned 400, so an invalid or expired OTP looked like a broken page.
The backend returns the reason (ERR_AUTH_002 invalid / ERR_AUTH_003
expired) in errors[].message, forwarded by the route; show it via toast.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>