feat: Implement favorites management API; add endpoints for adding, removing, and retrieving favorites for sounds and playlists

feat: Create Favorite model and repository for managing user favorites in the database
feat: Add FavoriteService to handle business logic for favorites management
feat: Enhance Playlist and Sound response schemas to include favorite indicators and counts
refactor: Update API routes to include favorites functionality in playlists and sounds

app/models/sound.py

@@ -6,6 +6,7 @@ from app.models.base import BaseModel
 
 if TYPE_CHECKING:
     from app.models.extraction import Extraction
+    from app.models.favorite import Favorite
     from app.models.playlist_sound import PlaylistSound
     from app.models.sound_played import SoundPlayed
 
@@ -36,3 +37,4 @@ class Sound(BaseModel, table=True):
     playlist_sounds: list["PlaylistSound"] = Relationship(back_populates="sound")
     extractions: list["Extraction"] = Relationship(back_populates="sound")
     play_history: list["SoundPlayed"] = Relationship(back_populates="sound")
+    favorites: list["Favorite"] = Relationship(back_populates="sound")