The Windows executable carried no icon, so Explorer, the taskbar, the
Start-menu tile and file-association entries showed a generic icon. Embed
AppIcon.ico via winresource in build.rs, and generate the .ico from the logo
before the build (it was produced after the build, too late to embed). Local
and non-Windows builds skip the step when the .ico is absent.
Fixes#107.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>