Adjust the backup and restore features to work with the .json format, including the data-karyawan-backup.json file.

To-do:

• On backup, copy data-karyawan.json to data-karyawan-backup.json.
• On restore, read the content of data-karyawan-backup.json and overwrite data-karyawan.json.
• Add confirmation before restoring (because it will overwrite the main file).
• Show success or failure messages.