BertBrowser 1.0.0

Velopack installer with auto-updates

- App data moves to ~/.bertbrowser (install dir %LOCALAPPDATA%\BertBrowser
  now belongs to Velopack); one-time migration from the old location
- Custom Main runs VelopackApp hooks; UpdateService downloads updates from
  GitHub Releases and always applies them on exit (restart prompt optional)
- App icon, scripts/pack.ps1 for local packing, tag-triggered release workflow

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>