fix: offload large UTF-8 decoding to background isolate

Prevents ANR when Dio's responseDecoder synchronously decodes large API
responses on the main thread. Responses >50KB use compute(). Also caches
MediaCodecList query results in ExoPlayerCore companion object.

lib/services/plex_client.dart

@@ -1,9 +1,12 @@
+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';
 
 import '../models/livetv_channel.dart';
@@ -109,6 +112,11 @@ class ConnectionTestResult {
   ConnectionTestResult({required this.success, required this.latencyMs, this.error});
 }
 
+// Top-level function required by compute()
+String _decodeUtf8(List<int> bytes) {
+  return utf8.decode(bytes, allowMalformed: true);
+}
+
 class PlexClient {
   PlexConfig config;
   late final Dio _dio;
@@ -136,8 +144,12 @@ class PlexClient {
   /// Get current offline mode state
   bool get isOfflineMode => _offlineMode;
 
-  /// Custom response decoder that handles malformed UTF-8 gracefully
-  static String _lenientUtf8Decoder(List<int> responseBytes, RequestOptions _, ResponseBody _) {
+  /// 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 __) {
+    if (responseBytes.length > 50 * 1024) {
+      return compute(_decodeUtf8, responseBytes);
+    }
     return utf8.decode(responseBytes, allowMalformed: true);
   }