Add immediate session timeouts

Currently, the Bitwarden Authenticator app will not consistently lock and prompt the user to reauthenticate with their biometric ID after leaving then opening the app. The behavior I expected for this feature is for it to be identical to the mobile password manager app, where the app is always locked after leaving it and I am immediately prompted to reauthenticate with my biometric ID.

To reproduce:

  1. Download Bitwarden Authenticator
  2. Skip the launch tutorial and go to Settings
  3. Enable biometric login (e.g., Unlock with Touch ID)
  4. Leave the app
  5. Open the app

Version: 2023.5.0 (23)
OS: iOS 17.4.1
Model: iPhone SE