Prefer biometric unlock

This implements the feature request from #2105 It adds a new preference option to prefer biometric unlock if auto-prompt is enabled AND biometric prompt was used to unlock the device previously. This results in getting the biometric prompt when unlocking the db after unlocking the phone, but not if the db was manually locked via the lock icon. Honestly, I'm not really sure it is necessary to hide this behind a setting, as the feature feels intuitive to me, but I added the setting to preserve the existing behavior.