refactor(core): reduce generated and duplicate code

lib/services/cover_cache_manager.dart

@@ -216,16 +216,4 @@ class CacheStats {
   final int totalSizeBytes;
 
   const CacheStats({required this.fileCount, required this.totalSizeBytes});
-
-  String get formattedSize {
-    if (totalSizeBytes < 1024) {
-      return '$totalSizeBytes B';
-    } else if (totalSizeBytes < 1024 * 1024) {
-      return '${(totalSizeBytes / 1024).toStringAsFixed(1)} KB';
-    } else if (totalSizeBytes < 1024 * 1024 * 1024) {
-      return '${(totalSizeBytes / (1024 * 1024)).toStringAsFixed(1)} MB';
-    } else {
-      return '${(totalSizeBytes / (1024 * 1024 * 1024)).toStringAsFixed(2)} GB';
-    }
-  }
 }

lib/services/history_database.dart

@@ -4,6 +4,7 @@ import 'package:sqflite/sqflite.dart';
 import 'package:path_provider/path_provider.dart';
 import 'package:shared_preferences/shared_preferences.dart';
 import 'package:spotiflac_android/services/sqlite_helpers.dart' as sqlite;
+import 'package:spotiflac_android/utils/isrc_utils.dart' as isrc;
 import 'package:spotiflac_android/utils/logger.dart';
 import 'package:spotiflac_android/utils/path_match_keys.dart';
 
@@ -286,9 +287,7 @@ class HistoryDatabase {
   static String normalizeLookupText(String? value) =>
       sqlite.normalizeLookupText(value);
 
-  static String normalizeIsrc(String? value) {
-    return (value ?? '').trim().toUpperCase().replaceAll(RegExp(r'[-\s]'), '');
-  }
+  static String normalizeIsrc(String? value) => isrc.normalizeIsrc(value);
 
   static String normalizeSpotifyId(String? value) {
     return (value ?? '').trim().toLowerCase();

lib/services/library_database_models.dart

@@ -240,8 +240,6 @@ class LocalLibrarySource {
 
 enum LocalLibrarySortMode { album, title, artist, latest, quality }
 
-enum LocalLibraryFilterMode { all, albums, singles }
-
 class LocalLibraryLookupIndex {
   final Set<String> isrcs;
   final Set<String> matchKeys;