A local device lock. Require a PIN to open ShowUP, pair it with Face ID, and blur content in the app switcher. This lock never leaves the phone.
Notes. The PIN is verified locally only — it is never sent to or checked against the server, so there is nothing to leak and nothing to reset. This is a physical- access defence, not an account defence: it protects against the person who picks up your unlocked phone at a bar, which for this product's threat model is a more likely event than a remote attacker.