Added a toggle to choose between using Artist property or AlbumArtist property for folder name (#169)

* Corrected function call to correctly download albums vs playlists

* Added setting to prefer AlbumArtist as folder name.
  - In practice, this prevents albums with multiple artists, featured artists, collaborations, or collections like soundtracks, from being split up
  - This is occasionally desirable behavior, so I added it as a toggle rather than a default behavior

frontend/src/lib/settings.ts

@@ -21,6 +21,7 @@ export interface Settings {
   filenameTemplate: string;
   // Legacy settings (kept for migration)
   filenameFormat?: "title-artist" | "artist-title" | "title";
+  useAlbumArtist?: boolean;
   artistSubfolder?: boolean;
   albumSubfolder?: boolean;
   trackNumber: boolean;