Support automatic updates

[matifali]

Implement an automatic update mechanism for Coder Desktop that:

• Checks for updates in the background
• Downloads updates silently
• Applies updates automatically or prompts the user to restart when needed

Requirements

• Update Mechanism
  • Implement an auto-update process using a framework like Sparkle
• UI
  • Add an “Auto-update” toggle in the preferences
  • Provide a way to check for updates manually

Example page from Tailscale macOS client.