chore: cleanup unused code and dead imports

lib/models/settings.dart

@@ -12,27 +12,27 @@ class AppSettings {
   final bool embedLyrics;
   final bool maxQualityCover;
   final bool isFirstLaunch;
-  final int concurrentDownloads; // 1 = sequential (default), max 3
-  final bool checkForUpdates; // Check for updates on app start
-  final String updateChannel; // stable, preview
-  final bool hasSearchedBefore; // Hide helper text after first search
-  final String folderOrganization; // none, artist, album, artist_album
-  final String historyViewMode; // list, grid
-  final String historyFilterMode; // all, albums, singles
-  final bool askQualityBeforeDownload; // Show quality picker before each download
-  final String spotifyClientId; // Custom Spotify client ID (empty = use default)
-  final String spotifyClientSecret; // Custom Spotify client secret (empty = use default)
-  final bool useCustomSpotifyCredentials; // Whether to use custom credentials (if set)
-  final String metadataSource; // spotify, deezer - source for search and metadata
-  final bool enableLogging; // Enable detailed logging for debugging
-  final bool useExtensionProviders; // Use extension providers for downloads when available
-  final String? searchProvider; // null/empty = default (Deezer/Spotify), otherwise extension ID
-  final bool separateSingles; // Separate singles/EPs into their own folder
-  final String albumFolderStructure; // artist_album, album_only, artist_year_album, year_album
-  final bool showExtensionStore; // Show Extension Store tab in navigation
-  final String locale; // App language: 'system', 'en', 'id', etc.
-  final bool enableMp3Option; // Enable MP3 quality option (default off, requires FFmpeg conversion)
-  final String lyricsMode; // embed, external, both - how to save lyrics
+  final int concurrentDownloads;
+  final bool checkForUpdates;
+  final String updateChannel;
+  final bool hasSearchedBefore;
+  final String folderOrganization;
+  final String historyViewMode;
+  final String historyFilterMode;
+  final bool askQualityBeforeDownload;
+  final String spotifyClientId;
+  final String spotifyClientSecret;
+  final bool useCustomSpotifyCredentials;
+  final String metadataSource;
+  final bool enableLogging;
+  final bool useExtensionProviders;
+  final String? searchProvider;
+  final bool separateSingles;
+  final String albumFolderStructure;
+  final bool showExtensionStore;
+  final String locale;
+  final bool enableMp3Option;
+  final String lyricsMode;
 
   const AppSettings({
     this.defaultService = 'tidal',
@@ -43,27 +43,27 @@ class AppSettings {
     this.embedLyrics = true,
     this.maxQualityCover = true,
     this.isFirstLaunch = true,
-    this.concurrentDownloads = 1, // Default: sequential (off)
-    this.checkForUpdates = true, // Default: enabled
-    this.updateChannel = 'stable', // Default: stable releases only
-    this.hasSearchedBefore = false, // Default: show helper text
-    this.folderOrganization = 'none', // Default: no folder organization
-    this.historyViewMode = 'grid', // Default: grid view
-    this.historyFilterMode = 'all', // Default: show all
-    this.askQualityBeforeDownload = true, // Default: ask quality before download
-    this.spotifyClientId = '', // Default: use built-in credentials
-    this.spotifyClientSecret = '', // Default: use built-in credentials
-    this.useCustomSpotifyCredentials = true, // Default: use custom if set
-    this.metadataSource = 'deezer', // Default: Deezer (no rate limit)
-    this.enableLogging = false, // Default: disabled for performance
-    this.useExtensionProviders = true, // Default: use extensions when available
-    this.searchProvider, // Default: null (use Deezer/Spotify)
-    this.separateSingles = false, // Default: disabled
-    this.albumFolderStructure = 'artist_album', // Default: Albums/Artist/Album
-    this.showExtensionStore = true, // Default: show store
-    this.locale = 'system', // Default: follow system language
-    this.enableMp3Option = false, // Default: disabled
-    this.lyricsMode = 'embed', // Default: embed lyrics into file
+    this.concurrentDownloads = 1,
+    this.checkForUpdates = true,
+    this.updateChannel = 'stable',
+    this.hasSearchedBefore = false,
+    this.folderOrganization = 'none',
+    this.historyViewMode = 'grid',
+    this.historyFilterMode = 'all',
+    this.askQualityBeforeDownload = true,
+    this.spotifyClientId = '',
+    this.spotifyClientSecret = '',
+    this.useCustomSpotifyCredentials = true,
+    this.metadataSource = 'deezer',
+    this.enableLogging = false,
+    this.useExtensionProviders = true,
+    this.searchProvider,
+    this.separateSingles = false,
+    this.albumFolderStructure = 'artist_album',
+    this.showExtensionStore = true,
+    this.locale = 'system',
+    this.enableMp3Option = false,
+    this.lyricsMode = 'embed',
   });
 
   AppSettings copyWith({
@@ -90,7 +90,7 @@ class AppSettings {
     bool? enableLogging,
     bool? useExtensionProviders,
     String? searchProvider,
-    bool clearSearchProvider = false, // Set to true to clear searchProvider to null
+    bool clearSearchProvider = false,
     bool? separateSingles,
     String? albumFolderStructure,
     bool? showExtensionStore,