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/slidingstackedwidget.cpp

@@ -1,4 +1,5 @@
 #include "slidingstackedwidget.h"
+#include "../tokens/AnimationTokens.h"
 #include <QWidget>
 #include <QLabel>
 #include <QScreen>
@@ -17,8 +18,8 @@ QPoint interpolatePoint(const QPoint &start, const QPoint &end, qreal progress)
 
 SlidingStackedWidget::SlidingStackedWidget(QWidget *parent)
     : QStackedWidget(parent),
-    m_speed(350), 
-    m_animationType(QEasingCurve::OutCubic), 
+    m_speed(AnimationTokens::DurationMs::kSlow), 
+    m_animationType(AnimationTokens::Curve::enter().type()), 
     m_isAnimating(false),
     m_nextIndex(0)
 {
@@ -45,6 +46,35 @@ void SlidingStackedWidget::slideInWgt(QWidget *widget, SlideDirection direction)
     }
 }
 
+void SlidingStackedWidget::jumpToWgt(QWidget *widget)
+{
+    int idx = indexOf(widget);
+    if (idx != -1) {
+        jumpToIdx(idx);
+    }
+}
+
+void SlidingStackedWidget::jumpToIdx(int idx)
+{
+    if (idx < 0 || idx >= count())
+        return;
+
+    if (currentIndex() == idx && !m_isAnimating)
+        return;
+
+    if (m_isAnimating) {
+        m_slideTimer.stop();
+        animationDoneSlot();
+    }
+
+    m_nextIndex = idx;
+    setCurrentIndex(idx);
+    QWidget *w = widget(idx);
+    if (w) w->raise();
+    flushPendingWidgetDisposals();
+    Q_EMIT animationFinished();
+}
+
 void SlidingStackedWidget::slideInIdx(int idx, SlideDirection direction)
 {
     if (idx < 0 || idx >= count())
@@ -55,21 +85,16 @@ void SlidingStackedWidget::slideInIdx(int idx, SlideDirection direction)
         return;
 
     
-    
+
     if (m_isAnimating) {
         m_slideTimer.stop();
-        animationDoneSlot();           
+        animationDoneSlot();
     }
 
-    
+
     bool reduceAnimations = ConfigStore::instance()->get<bool>(ConfigKeys::UiAnimations, false);
     if (reduceAnimations) {
-        m_nextIndex = idx;
-        setCurrentIndex(idx);
-        QWidget *w = widget(idx);
-        if (w) w->raise();
-        flushPendingWidgetDisposals();
-        Q_EMIT animationFinished();
+        jumpToIdx(idx);
         return;
     }