fix: preserve home screen scroll position on back navigation

lib/mixins/tab_visibility_aware.dart

@@ -3,6 +3,6 @@
 /// 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 onTabShown({bool scrollToTop = true});
   void onTabHidden();
 }

lib/screens/discover_screen.dart

@@ -379,11 +379,13 @@ class _DiscoverScreenState extends State<DiscoverScreen>
   }
 
   @override
-  void onTabShown() {
+  void onTabShown({bool scrollToTop = true}) {
     if (!_isAutoScrollPaused) {
       _startAutoScroll();
     }
-    _focusTopBoundary();
+    if (scrollToTop) {
+      _focusTopBoundary();
+    }
   }
 
   // Helper method to calculate visible dot range (max 5 dots)

lib/screens/main_screen.dart

@@ -796,7 +796,7 @@ class _MainScreenState extends State<MainScreen> with RouteAware, WindowListener
     // 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();
+        aware.onTabShown(scrollToTop: false);
       }
       _onDiscoverBecameVisible();
     }

lib/services/plex_client.dart

@@ -2,9 +2,6 @@ import 'dart:async';
 import 'dart:convert';
 import 'dart:isolate';
 import 'dart:math';
-import 'dart:typed_data';
-import 'dart:ui' show VoidCallback;
-
 import 'package:flutter/foundation.dart';
 
 import 'package:dio/dio.dart';
@@ -146,7 +143,7 @@ class PlexClient {
 
   /// Custom response decoder that handles malformed UTF-8 gracefully.
   /// Large responses are decoded in a background isolate to avoid ANR.
-  static FutureOr<String> _lenientUtf8Decoder(List<int> responseBytes, RequestOptions _, ResponseBody __) {
+  static FutureOr<String> _lenientUtf8Decoder(List<int> responseBytes, RequestOptions _, ResponseBody _a) {
     if (responseBytes.length > 50 * 1024) {
       return compute(_decodeUtf8, responseBytes);
     }