Each session renewal issues a PIN with fresh attempts, so without a limit a stolen session could keep guessing. The quota is separate from the one for renewals without a session, so neither can use up the other's.
Replace AUTH_GUEST_SESSION_JWT_SECRET with a key derived via
HMAC-SHA256 from the reva JWT secret. Guest session tokens and reva
access tokens remain unforgeable across each other without a second
secret to configure.