perf: smooth UI animations and reduce repaint overhead

Batch of performance and animation work: shared FadeHelper/MotionPrefs
primitives, hover animators, shadow pixmap caching, smooth scrolling,
seek time bubble, and widespread component repaint reductions.

src/qEmbyApp/components/libraryactionmenu.cpp

@@ -1,6 +1,7 @@
 #include "libraryactionmenu.h"
 
 #include "../managers/thememanager.h"
+#include "../utils/popupfade.h"
 #include <QAction>
 #include <QFile>
 #include <QIcon>
@@ -16,6 +17,8 @@ LibraryActionMenu::LibraryActionMenu(const VirtualFolder& folder,
                    Qt::NoDropShadowWindowHint);
     setAttribute(Qt::WA_TranslucentBackground);
 
+    PopupFade::attach(this);
+
     setupMenu();
 }