feat(desktop): implement auto-update functionality

[Red-Asuka]

PR Checklist

What is the new behavior?

• Completely isolate the main process from the rendering layer logic for a more optimized code structure.
• Adapt the update notification pop-up to align with the theme style.
• Add “Already up to date, no update needed” notification.
• Improve the cancel download functionality.
• Ensure the update log window remains always on top.

Note: Your application must be signed for automatic updates on macOS. This is a requirement of Squirrel.Mac.

Based on the reasons above, we will temporarily hold off on testing the complete update process. We will conduct unified testing once the development of v2.0.0 is substantially completed.

Does this PR introduce a breaking change?

• Yes
• No

Specific Instructions

Are there any specific instructions or things that should be known prior to review?

Other information