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/views/admin/nowplayingcard.h

@@ -10,6 +10,7 @@ struct SessionInfo;
 class QEmbyCore;
 class QLabel;
 class QProgressBar;
+class TweenedValue;
 
 class NowPlayingCard : public QFrame {
     Q_OBJECT
@@ -38,6 +39,7 @@ private:
     QProgressBar* m_progressBar;
     QLabel* m_userLabel;
     QLabel* m_streamLabel;
+    TweenedValue* m_progressTween = nullptr;
 };
 
 #endif