fix: stabilize IPTV playback and implement request throttling

- Add playback lock to XtreamService to delay EPG during stream init
- Increase MPEG-TS stash buffer to 512KB for better stability
- Enable liveBufferLatencyChasing to prevent stream drift
- Tune HLS parameters for balanced speed and reliability

lib/features/iptv/screens/player_screen.dart

@@ -140,6 +140,12 @@ class _PlayerScreenState extends ConsumerState<PlayerScreen> {
         streamUrl = service.getLiveStreamUrlTs(currentStreamId);
       }
 
+      // STABILIZATION: Lock background requests during stream init
+      service.isPlaybackLoading = true;
+      Future.delayed(const Duration(seconds: 10), () {
+        service.isPlaybackLoading = false;
+      });
+
       _currentStreamUrl = streamUrl;
 
       final encodedUrl = Uri.encodeComponent(streamUrl);

lib/features/iptv/services/xtream_service.dart

@@ -15,6 +15,13 @@ class XtreamService {
 
   PlaylistConfig? _currentPlaylist;
 
+  /// Flag to indicate that a playback is currently loading
+  /// Used to throttle background requests (EPG, images)
+  bool isPlaybackLoading = false;
+
+  /// Minimum delay for background requests when playback is loading
+  static const _throttleDelay = Duration(seconds: 8);
+
   XtreamService() {
     _dio = Dio(
       BaseOptions(
@@ -616,6 +623,11 @@ class XtreamService {
   Future<List<EpgEntry>> getShortEpg(String streamId) async {
     if (_currentPlaylist == null) throw Exception('No playlist configured');
 
+    if (isPlaybackLoading) {
+      debugPrint('[XtreamService] Throttling short EPG for $streamId');
+      await Future.delayed(_throttleDelay);
+    }
+
     try {
       final response = await _dio.get(
         _wrapWithProxy(_currentPlaylist!.apiBaseUrl),
@@ -653,6 +665,11 @@ class XtreamService {
   Future<xm.ShortEPG> getShortEPG(String streamId) async {
     if (_currentPlaylist == null) throw Exception('No playlist configured');
 
+    if (isPlaybackLoading) {
+      debugPrint('[XtreamService] Throttling short EPG metadata for $streamId');
+      await Future.delayed(_throttleDelay);
+    }
+
     try {
       final response = await _dio.get(
         _wrapWithProxy(_currentPlaylist!.apiBaseUrl),