Check passcode authenticity using SHA256 hexdigest instead of plain comparison

You can find reference on how hashes can be generated here https://stackoverflow.com/questions/18338890/are-there-any-sha-256-javascript-implementations-that-are-generally-considered-t/48161723#48161723.

Generate the hexdigest during login and keep exchanging it every now and then instead of converting it to a hexdigest on every request to make transactions efficient.

Start by tracing the login flow and locating the current plain passcode comparison. Review the linked SHA-256 reference, then determine how the hexdigest should be generated at login and exchanged periodically. Done means authentication no longer compares the passcode directly and the exchange behavior is covered by the existing project checks.

Written by the indexing model from the issue text.