fix: preserve extended metadata during fallback, accurate lossy quality display, SAF improvements

- Add Genre/Label/Copyright fields to DownloadResult struct
- buildDownloadSuccessResponse now prefers service result metadata over request
- enrichRequestExtendedMetadata fetches Deezer metadata by ISRC before download
- Flutter sends copyright in download request payload
- History merge preserves existing genre/label/copyright on re-download
- Accurate MP3 duration via Xing/VBRI VBR headers, MPEG2/2.5 bitrate tables
- Accurate Opus/Vorbis duration via last Ogg page granule position
- Bitrate field added to LibraryScanResult, LocalLibraryItem, DB v4 migration
- Lossy formats display format+bitrate instead of fake 16-bit quality
- Local library file date uses fileModTime instead of scannedAt
- SAF URI recovery for transient FD paths after download
- Improved SAF repair and download history path matching in library scan
- Extract quality probe logic into reusable enrichResultQualityFromFile

lib/services/library_database.dart

@@ -23,6 +23,7 @@ class LocalLibraryItem {
   final String? releaseDate;
   final int? bitDepth;
   final int? sampleRate;
+  final int? bitrate; // kbps, for lossy formats (mp3, opus, ogg)
   final String? genre;
   final String? format; // flac, mp3, opus, m4a
 
@@ -43,6 +44,7 @@ class LocalLibraryItem {
     this.releaseDate,
     this.bitDepth,
     this.sampleRate,
+    this.bitrate,
     this.genre,
     this.format,
   });
@@ -64,6 +66,7 @@ class LocalLibraryItem {
     'releaseDate': releaseDate,
     'bitDepth': bitDepth,
     'sampleRate': sampleRate,
+    'bitrate': bitrate,
     'genre': genre,
     'format': format,
   };
@@ -86,6 +89,7 @@ class LocalLibraryItem {
         releaseDate: json['releaseDate'] as String?,
         bitDepth: json['bitDepth'] as int?,
         sampleRate: json['sampleRate'] as int?,
+        bitrate: (json['bitrate'] as num?)?.toInt(),
         genre: json['genre'] as String?,
         format: json['format'] as String?,
       );
@@ -115,7 +119,7 @@ class LibraryDatabase {
     
     return await openDatabase(
       path,
-      version: 3, // Bumped version for file_mod_time migration
+      version: 4, // Bumped version for bitrate column
       onCreate: _createDB,
       onUpgrade: _upgradeDB,
     );
@@ -142,6 +146,7 @@ class LibraryDatabase {
         release_date TEXT,
         bit_depth INTEGER,
         sample_rate INTEGER,
+        bitrate INTEGER,
         genre TEXT,
         format TEXT
       )
@@ -169,6 +174,12 @@ class LibraryDatabase {
       await db.execute('ALTER TABLE library ADD COLUMN file_mod_time INTEGER');
       _log.i('Added file_mod_time column for incremental scanning');
     }
+    
+    if (oldVersion < 4) {
+      // Add bitrate column for lossy format quality info
+      await db.execute('ALTER TABLE library ADD COLUMN bitrate INTEGER');
+      _log.i('Added bitrate column for lossy format quality');
+    }
   }
   
   Map<String, dynamic> _jsonToDbRow(Map<String, dynamic> json) {
@@ -189,6 +200,7 @@ class LibraryDatabase {
       'release_date': json['releaseDate'],
       'bit_depth': json['bitDepth'],
       'sample_rate': json['sampleRate'],
+      'bitrate': json['bitrate'],
       'genre': json['genre'],
       'format': json['format'],
     };
@@ -212,6 +224,7 @@ class LibraryDatabase {
       'releaseDate': row['release_date'],
       'bitDepth': row['bit_depth'],
       'sampleRate': row['sample_rate'],
+      'bitrate': row['bitrate'],
       'genre': row['genre'],
       'format': row['format'],
     };

lib/services/platform_bridge.dart

@@ -103,8 +103,6 @@ class PlatformBridge {
     return response;
   }
 
-
-
   static Future<Map<String, dynamic>> getDownloadProgress() async {
     final result = await _channel.invokeMethod('getDownloadProgress');
     return jsonDecode(result as String) as Map<String, dynamic>;
@@ -509,6 +507,7 @@ class PlatformBridge {
       return {
         'genre': data['genre'] as String? ?? '',
         'label': data['label'] as String? ?? '',
+        'copyright': data['copyright'] as String? ?? '',
       };
     } catch (e) {
       _log.w('Failed to get Deezer extended metadata for $trackId: $e');
@@ -719,8 +718,6 @@ class PlatformBridge {
     return list.map((e) => e as Map<String, dynamic>).toList();
   }
 
-
-
   static Future<void> cleanupExtensions() async {
     _log.d('cleanupExtensions');
     await _channel.invokeMethod('cleanupExtensions');
@@ -1130,5 +1127,4 @@ class PlatformBridge {
   }
 
   // ==================== YOUTUBE / COBALT ====================
-
 }