v3.18.32 — Fix: cart & favorites guest 403s

Extends retry-with-fresh-nonce to dd_cart_update, dd_cart_remove (both callers), dd_cart_get, and dd_save_favorites. dd_track_event intentionally left untouched — server always returns success:true even on nonce failure, so no client retry is possible until the server itself is fixed (separate future release). See RELEASE.md.