Fix: Liked songs not playing as a playlist

[theovilardo]

This commit resolves an issue where the 'Liked Songs' list in the library did not function as a self-contained playlist.

Previously, playing a song from the 'Liked' tab or using the shuffle button would incorrectly include all songs from the library in the playback queue.

This has been fixed by:

• Adding a shuffleFavoriteSongs() function to PlayerViewModel to specifically handle shuffling of the liked songs list.
• Updating LibraryScreen.kt to call the new shuffle function when the shuffle button is pressed on the 'Liked' tab.
• Modifying the song item's click handler in the 'Liked' tab to call showAndPlaySong with the favoriteSongs list, ensuring the playback queue is correctly limited to only liked songs.