Update credentials

Update password

Look for the password manager's main script and the function that handles password storage. The issue likely requires adding an 'update' operation to the existing 'add' and 'retrieve' commands. Check how credentials are currently stored (e.g., a JSON file or database) and write a function to modify an existing entry. Test by running the CLI and verifying the update works.

索引モデルが issue の本文から書いたものです。