feat: add YouTube provider for lossy downloads via Cobalt API

- New YouTube download provider with Opus 256kbps and MP3 320kbps options
- SongLink/Odesli integration for Spotify/Deezer ID to YouTube URL conversion
- YouTube video ID detection for YT Music extension compatibility
- Parallel cover art and lyrics fetching during download
- Queue progress shows bytes (X.X MB) for streaming downloads
- Full metadata embedding: cover, lyrics, title, artist, album, track#, disc#, year, ISRC
- Removed Tidal HIGH (lossy AAC) option - use YouTube for lossy instead
- Bumped version to 3.6.0

lib/models/download_item.dart

@@ -28,6 +28,7 @@ class DownloadItem {
   final DownloadStatus status;
   final double progress;
   final double speedMBps;
+  final int bytesReceived; // Bytes downloaded so far (for unknown size downloads)
   final String? filePath;
   final String? error;
   final DownloadErrorType? errorType;
@@ -41,6 +42,7 @@ class DownloadItem {
     this.status = DownloadStatus.queued,
     this.progress = 0.0,
     this.speedMBps = 0.0,
+    this.bytesReceived = 0,
     this.filePath,
     this.error,
     this.errorType,
@@ -55,6 +57,7 @@ class DownloadItem {
     DownloadStatus? status,
     double? progress,
     double? speedMBps,
+    int? bytesReceived,
     String? filePath,
     String? error,
     DownloadErrorType? errorType,
@@ -68,6 +71,7 @@ class DownloadItem {
       status: status ?? this.status,
       progress: progress ?? this.progress,
       speedMBps: speedMBps ?? this.speedMBps,
+      bytesReceived: bytesReceived ?? this.bytesReceived,
       filePath: filePath ?? this.filePath,
       error: error ?? this.error,
       errorType: errorType ?? this.errorType,

lib/models/download_item.g.dart

@@ -15,6 +15,7 @@ DownloadItem _$DownloadItemFromJson(Map<String, dynamic> json) => DownloadItem(
       DownloadStatus.queued,
   progress: (json['progress'] as num?)?.toDouble() ?? 0.0,
   speedMBps: (json['speedMBps'] as num?)?.toDouble() ?? 0.0,
+  bytesReceived: (json['bytesReceived'] as num?)?.toInt() ?? 0,
   filePath: json['filePath'] as String?,
   error: json['error'] as String?,
   errorType: $enumDecodeNullable(_$DownloadErrorTypeEnumMap, json['errorType']),
@@ -30,6 +31,7 @@ Map<String, dynamic> _$DownloadItemToJson(DownloadItem instance) =>
       'status': _$DownloadStatusEnumMap[instance.status]!,
       'progress': instance.progress,
       'speedMBps': instance.speedMBps,
+      'bytesReceived': instance.bytesReceived,
       'filePath': instance.filePath,
       'error': instance.error,
       'errorType': _$DownloadErrorTypeEnumMap[instance.errorType],