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.cpp

@@ -4,6 +4,7 @@
 #include <services/media/mediaservice.h>
 #include "../../managers/thememanager.h"
 #include "../../utils/imageutils.h"
+#include "../../utils/tweenedvalue.h"
 
 #include <QFontMetrics>
 #include <QHBoxLayout>
@@ -86,6 +87,10 @@ void NowPlayingCard::setupUi(const SessionInfo& session) {
     m_progressBar->setRange(0, 1000);
     infoLayout->addWidget(m_progressBar);
 
+    m_progressTween = new TweenedValue(this);
+    connect(m_progressTween, &TweenedValue::valueChanged, this,
+            [this](qreal value) { m_progressBar->setValue(qRound(value)); });
+
     infoLayout->addSpacing(2);
 
     
@@ -151,7 +156,7 @@ void NowPlayingCard::updateSession(const SessionInfo& session) {
         m_stateIcon->setPixmap(stateIcon.pixmap(QSize(12, 12)));
 
         m_progressText->setText(posStr + " / " + durStr);
-        m_progressBar->setValue(static_cast<int>(session.playbackProgress() * 1000));
+        m_progressTween->setTarget(session.playbackProgress() * 1000);
         m_progressText->show();
         m_stateIcon->show();
         m_progressBar->show();