Fix thumbnail badge scaling on Retina displays

Synth and train track badges were drawn at a fixed pixel size before thumbnail downsampling, making them appear smaller on high-DPI displays.

Scale badge painting by the thumbnail device pixel ratio and enable smooth image transforms to preserve the apparent badge size across display scales.

common/lc_thumbnailmanager.cpp

@@ -436,6 +436,8 @@ void lcThumbnailManager::DrawThumbnail(lcPartThumbnailId ThumbnailId, lcPartThum
 			ImageBits += Icon.bytesPerLine();
 		}
 
+		Painter.setRenderHint(QPainter::SmoothPixmapTransform);
+		Painter.scale(Thumbnail.DeviceScale, Thumbnail.DeviceScale);
 		Painter.drawImage(QPoint(0, 0), Icon);
 		Painter.end();
 	}