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/media/detailview.cpp

@@ -1,4 +1,6 @@
 #include "detailview.h"
+#include "../../tokens/AnimationTokens.h"
+#include "../../utils/fadehelper.h"
 #include "../../components/detailactionwidget.h"
 #include "../../components/detailbottominfowidget.h"
 #include "../../components/detailcontentwidget.h"
@@ -463,7 +465,7 @@ void DetailView::setupUi() {
 
   m_vScrollController =
       new SmoothScrollController(m_mainScrollArea->verticalScrollBar(), this);
-  m_vScrollController->setDuration(170);
+  m_vScrollController->setDuration(AnimationTokens::DurationMs::kFast);
 
   m_contentWidget = new DetailContentWidget(m_mainScrollArea);
   m_contentWidget->setObjectName("detail-content-container");
@@ -1037,7 +1039,9 @@ QCoro::Task<void> DetailView::loadItem(const QString &itemId,
 
   
   
-  QTimer::singleShot(380, this, [safeThis, itemId]() {
+  // Guard tracks the page-slide duration (kSlow) so the poster shadow / deferred
+  // content reveal lands as the incoming slide settles; kept in sync via the token.
+  QTimer::singleShot(AnimationTokens::DurationMs::kSlow, this, [safeThis, itemId]() {
     if (!safeThis || safeThis->m_pendingDeferredFetchId != itemId)
       return;
     if (safeThis->m_posterShadow)
@@ -3253,7 +3257,8 @@ QCoro::Task<void> DetailView::executeLoadImages(QPointer<DetailView> safeThis,
   if (cachedImages.logo.has_value()) {
     safeThis->m_logoLabel->setPixmap(
         QPixmap::fromImage(cachedImages.logo.value()));
-    safeThis->m_logoLabel->show();
+    FadeHelper::fadeIn(safeThis->m_logoLabel,
+                       AnimationTokens::DurationMs::kNormal);
     qDebug() << "[DetailView] Detail logo image cache hit"
              << "itemId=" << item.id;
   }
@@ -3357,7 +3362,8 @@ QCoro::Task<void> DetailView::executeLoadImages(QPointer<DetailView> safeThis,
                 if (!result.isNull()) {
                   safeThis->m_logoLabel->setPixmap(
                       QPixmap::fromImage(result));
-                  safeThis->m_logoLabel->show();
+                  FadeHelper::fadeIn(safeThis->m_logoLabel,
+                                     AnimationTokens::DurationMs::kNormal);
                   saveDetailImageAsync(
                       cacheServerId, cacheUserId, currentItemId,
                       QStringLiteral("logo"), logoId, logoType, logoTag,