fix: suspend hero animation when not visible

lib/mixins/tab_visibility_aware.dart

@@ -0,0 +1,8 @@
+/// Mixin for screens that need to react to tab visibility changes.
+///
+/// Used by MainScreen to pause expensive work (e.g. animation tickers)
+/// when the screen's tab is no longer visible, and resume it when shown again.
+mixin TabVisibilityAware {
+  void onTabShown();
+  void onTabHidden();
+}

lib/screens/discover_screen.dart

@@ -22,6 +22,7 @@ import 'profile/profile_switch_screen.dart';
 import '../providers/user_profile_provider.dart';
 import '../providers/settings_provider.dart';
 import '../mixins/refreshable.dart';
+import '../mixins/tab_visibility_aware.dart';
 import '../i18n/strings.g.dart';
 import '../mixins/item_updatable.dart';
 import '../mixins/watch_state_aware.dart';
@@ -53,6 +54,7 @@ class _DiscoverScreenState extends State<DiscoverScreen>
         FullRefreshable,
         ItemUpdatable,
         WatchStateAware,
+        TabVisibilityAware,
         SingleTickerProviderStateMixin,
         WidgetsBindingObserver {
   static const Duration _heroAutoScrollDuration = Duration(seconds: 8);
@@ -470,6 +472,19 @@ class _DiscoverScreenState extends State<DiscoverScreen>
     _startAutoScroll();
   }
 
+  @override
+  void onTabHidden() {
+    _autoScrollTimer?.cancel();
+    _indicatorAnimationController.stop();
+  }
+
+  @override
+  void onTabShown() {
+    if (!_isAutoScrollPaused) {
+      _startAutoScroll();
+    }
+  }
+
   // Helper method to calculate visible dot range (max 5 dots)
   ({int start, int end}) _getVisibleDotRange() {
     final totalDots = _onDeck.length;
@@ -1277,9 +1292,7 @@ class _DiscoverScreenState extends State<DiscoverScreen>
                               final maxWidth = dotSize * 3; // 24px for normal, 15px for small
                               final fillWidth = dotSize + ((maxWidth - dotSize) * _indicatorAnimationController.value);
                               final onSurface = Theme.of(context).colorScheme.onSurface;
-                              return AnimatedContainer(
-                                duration: tokens(context).slow,
-                                curve: Curves.easeInOut,
+                              return Container(
                                 margin: const EdgeInsets.symmetric(horizontal: 4),
                                 width: maxWidth,
                                 height: dotSize,

lib/screens/main_screen.dart

@@ -14,6 +14,7 @@ import '../utils/platform_detector.dart';
 import '../utils/video_player_navigation.dart';
 import '../main.dart';
 import '../mixins/refreshable.dart';
+import '../mixins/tab_visibility_aware.dart';
 import '../navigation/navigation_tabs.dart';
 import '../providers/multi_server_provider.dart';
 import '../providers/server_state_provider.dart';
@@ -495,10 +496,23 @@ class _MainScreenState extends State<MainScreen> with RouteAware, WindowListener
     }
   }
 
+  @override
+  void didPushNext() {
+    // Called when a child route is pushed on top (e.g., video player)
+    if (_currentIndex == 0 && !_isOffline) {
+      if (_discoverKey.currentState case final TabVisibilityAware aware) {
+        aware.onTabHidden();
+      }
+    }
+  }
+
   @override
   void didPopNext() {
     // Called when returning to this route from a child route (e.g., from video player)
     if (_currentIndex == 0 && !_isOffline) {
+      if (_discoverKey.currentState case final TabVisibilityAware aware) {
+        aware.onTabShown();
+      }
       _onDiscoverBecameVisible();
     }
   }
@@ -593,8 +607,19 @@ class _MainScreenState extends State<MainScreen> with RouteAware, WindowListener
 
     // Skip online-only screen logic in offline mode
     if (!_isOffline) {
+      // Pause/resume discover auto-scroll when switching tabs
+      if (previousIndex == 0 && index != 0) {
+        if (_discoverKey.currentState case final TabVisibilityAware aware) {
+          aware.onTabHidden();
+        }
+      }
       // Notify discover screen when it becomes visible via tab switch
       if (index == 0) {
+        if (previousIndex != 0) {
+          if (_discoverKey.currentState case final TabVisibilityAware aware) {
+            aware.onTabShown();
+          }
+        }
         _onDiscoverBecameVisible();
       }
       // Ensure the libraries screen applies focus when brought into view