Update Stripe API Keys on Custom Larval App

Update current checkout/payment integration to use the new ShipCargo Stripe account credentials. Scope: Replace existing Stripe API keys with new production keys Update: secret key publishable key webhook secret(s) if applicable Verify all current checkout/payment flows continue functioning correctly after update Please test: checkout creation payment success flow webhook events order confirmation flow failed payment handling Important: Ensure old Stripe account is fully disconnected from production environment Confirm no hardcoded keys remain in frontend/backend Store keys in proper environment variables/config This ticket is only for updating Stripe account/API credentials on the current live checkout flow.