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/playerosdlayer.cpp

@@ -1,4 +1,6 @@
 #include "playerosdlayer.h"
+#include "../tokens/AnimationTokens.h"
+#include "../utils/motionprefs.h"
 #include <QAbstractAnimation>
 #include <QGraphicsOpacityEffect>
 #include <QIcon>
@@ -56,7 +58,8 @@ PlayerOsdLayer::PlayerOsdLayer(QWidget *parent)
 
     
     m_fadeAnim = new QPropertyAnimation(m_opacity, "opacity", this);
-    m_fadeAnim->setDuration(250);
+    m_fadeAnim->setDuration(AnimationTokens::DurationMs::kNormal);
+    m_fadeAnim->setEasingCurve(AnimationTokens::Curve::fade());
 
     
     m_hideTimer = new QTimer(this);
@@ -276,7 +279,7 @@ void PlayerOsdLayer::fadeIn()
 
 bool PlayerOsdLayer::canStartAnimation() const
 {
-    return m_fadeAnim && m_fadeAnim->targetObject();
+    return m_fadeAnim && m_fadeAnim->targetObject() && !MotionPrefs::reduceMotion();
 }
 
 void PlayerOsdLayer::updateSeekLayout()