feat: implement silent background auto-updater for GitHub releases

[Fearcine]

Summary

Implemented a silent background auto-updater for GitHub Releases to mirror the seamless update experience.

Motivation

The current self-compiled / GitHub Release version of the app was not updating itself and had to do it manually. This PR introduces a background update mechanism that downloads and applies updates without conflicting with the native auto-update behavior of the Microsoft Store version.

Type of Change

• Feature
• Bug fix
• Refactor (no functional changes)
• Style (formatting, naming)
• Other

What Changed

• Added a new service that periodically checks the GitHub API and downloads .msix packages in the background.
• Added download progress UI and a "Restart" action button to the Home Page update card.
• Added an "Auto-update" toggle to System Settings (enabled by default)
• Added a Windows Toast notification to prompt the user to restart the app once an update has been successfully staged.
• Guarded the entire implementation behind the #if GITHUB_RELEASE constant to guarantee zero interference with Microsoft Store builds.

Additional Information

Checklist

• Code changes are manually tested and working.
• Formatting and naming are consistent with the project.
• Self-review of changes is done.

• AI tools were used (if yes, I reviewed and fully understand the changes myself).