refactor: deduplicate shared patterns, replace hardcoded colors

lib/models/plex_media_info.dart

@@ -1,5 +1,6 @@
 import '../utils/app_logger.dart';
 import '../utils/codec_utils.dart';
+import '../utils/track_label_builder.dart' show buildTrackLabel;
 
 class PlexMediaInfo {
   final String videoUrl;
@@ -23,9 +24,9 @@ class PlexMediaInfo {
   static PlexMediaInfo? fromMetadataJson(Map<String, dynamic> metadata) {
     final media = metadata['Media'] as List<dynamic>?;
     if (media == null || media.isEmpty) return null;
-    final parts = media[0]['Part'] as List<dynamic>?;
+    final parts = media.first['Part'] as List<dynamic>?;
     if (parts == null || parts.isEmpty) return null;
-    final streams = parts[0]['Stream'] as List<dynamic>?;
+    final streams = parts.first['Stream'] as List<dynamic>?;
 
     final audioTracks = <PlexAudioTrack>[];
     final subtitleTracks = <PlexSubtitleTrack>[];
@@ -75,27 +76,11 @@ class PlexMediaInfo {
   }
 }
 
-/// Builds a track label from parts with the standard `' · '` joiner pattern.
+/// Mixin for building track labels with a consistent pattern.
 ///
-/// Shared by both Plex track models and MPV track label utilities.
-/// If [title] is non-empty it is added first, then [language], then [extraParts].
-/// Falls back to `'$fallbackPrefix ${index + 1}'` when no parts are available.
-String buildTrackLabel({
-  String? title,
-  String? language,
-  List<String> extraParts = const [],
-  required int index,
-  String fallbackPrefix = 'Track',
-}) {
-  final parts = <String>[];
-  if (title != null && title.isNotEmpty) parts.add(title);
-  if (language != null && language.isNotEmpty) parts.add(language);
-  parts.addAll(extraParts);
-  return parts.isEmpty ? '$fallbackPrefix ${index + 1}' : parts.join(' · ');
-}
-
-/// Mixin for building track labels with a consistent pattern
-mixin TrackLabelBuilder {
+/// Used by [PlexAudioTrack] and [PlexSubtitleTrack] to provide a [buildLabel]
+/// method that delegates to the shared [buildTrackLabel] function.
+mixin _TrackLabelMixin {
   int get id;
   int? get index;
   String? get displayTitle;
@@ -112,7 +97,7 @@ mixin TrackLabelBuilder {
   }
 }
 
-class PlexAudioTrack with TrackLabelBuilder {
+class PlexAudioTrack with _TrackLabelMixin {
   @override
   final int id;
   @override
@@ -147,7 +132,7 @@ class PlexAudioTrack with TrackLabelBuilder {
   }
 }
 
-class PlexSubtitleTrack with TrackLabelBuilder {
+class PlexSubtitleTrack with _TrackLabelMixin {
   @override
   final int id;
   @override