fix(settings): download updates in-app with progress instead of opening website

[kdroidFilter]

Summary

• The General Settings update banner now downloads and installs updates in-app, matching the existing UpdateDialog flow, instead of opening the download website in a browser.
• Available → "Download now" triggers AppUpdateService.startDownload().
• Downloading → shows percentage + an AnimatedHorizontalProgressBar.
• ReadyToInstall → "Install and restart" triggers AppUpdateService.installAndRestart().
• The service is wired via LocalAppGraph and passed down as callbacks; @Preview keeps no-op defaults.
• Removed the now-unused browser fallback (UrlOpener.open(DOWNLOAD_URL)) for updates.

Test plan

• Settings shows "Download now" when an update is available
• Clicking it downloads in-app and shows a live progress bar
• Once downloaded, the banner offers "Install and restart" and relaunches correctly
• "Up to date" / "check failed" / "checking" states still render as before