Added 4 and 6 digit passcode length support and fix passcode length assumption on app update.

Addressed the issue where users updating to a new VLC release were inadvertently blocked from accessing the app due to a change in passcode length assumptions. Implemented a fix to ensure backward compatibility by retaining the passcode length configured by the user in previous versions. Now, users updating from versions with a 4-digit passcode will continue to use a 4-digit passcode, preventing any access disruptions.