Implement automatic update when main repository changes

[DutrieuxLU]

Feature Request: Auto-Update for ssh-grades

Summary:
Implement a mechanism in the ssh-grades program to automatically update itself whenever the main repository receives new changes (commits or releases).

Details:

• Monitor the main repository for updates (e.g., new commits to main branch, new releases).
• When an update is detected, trigger a process to update the local program (could be via git pull, download release, or other method).
• Ensure update process handles dependencies and avoids breaking changes.
• Optionally, notify the user when an update occurs or fails.

Benefits:

• Keeps ssh-grades up-to-date with the latest features and fixes.
• Reduces manual intervention for updates.

Implementation Notes:

• Consider using GitHub webhooks, scheduled jobs (cron), or a startup check.
• Log update events and errors for troubleshooting.

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This issue proposes adding an upgrade mechanism to streamline maintenance and improve user experience.