fix(gui): make SVG icon rasterization DPI-aware in loadPixmap (#189)

loadPixmap() rendered all SVGs at a hardcoded 64x64 pixels regardless of
display DPI. On HiDPI screens, Qt then downscaled these low-resolution
pixmaps to the toolbar icon size, producing chunky/aliased icons.

Multiply the render size by getMaximumDPR() and tag the resulting pixmap
with the correct devicePixelRatio, matching the pattern already used in
pixmapFromSvg(const char* name, QSizeF size). This ensures SVGs are
rasterized at the physical resolution needed for crisp display.

src/Gui/BitmapFactory.cpp

@@ -217,7 +217,9 @@ bool BitmapFactoryInst::loadPixmap(const QString& filename, QPixmap& icon) const
             QFile svgFile(fi.filePath());
             if (svgFile.open(QFile::ReadOnly | QFile::Text)) {
                 QByteArray content = svgFile.readAll();
-                icon = pixmapFromSvg(content, QSize(64, 64));
+                static qreal dpr = getMaximumDPR();
+                icon = pixmapFromSvg(content, QSize(64, 64) * dpr);
+                icon.setDevicePixelRatio(dpr);
             }
         }
         else {