Update AppImage icon source path in build workflow

Modified the build script to copy the application icon from the AppDir lib directory instead of the composeApp logo directory during the AppImage creation process.

Author: rainxchzed

.github/workflows/build-desktop-platforms.yml

@@ -250,7 +250,7 @@ jobs:
           EOF
 
           # Copy icon to AppDir root (required by appimagetool)
-          cp composeApp/logo/app_icon.png "$APPDIR/github-store.png"
+          cp "$APPDIR/lib/GitHub-Store.png" "$APPDIR/github-store.png"
 
           # Build .AppImage
           OUTPUT="composeApp/build/compose/binaries/main/GitHub-Store-x86_64.AppImage"