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/api/v1/playlists.py

@@ -19,6 +19,7 @@ from app.schemas.playlist import (
     PlaylistStatsResponse,
     PlaylistUpdateRequest,
 )
+from app.services.favorite import FavoriteService
 from app.services.playlist import PlaylistService
 
 router = APIRouter(prefix="/playlists", tags=["playlists"])
@@ -31,6 +32,12 @@ async def get_playlist_service(
     return PlaylistService(session)
 
 
+def get_favorite_service() -> FavoriteService:
+    """Get the favorite service."""
+    from app.core.database import get_session_factory
+    return FavoriteService(get_session_factory())
+
+
 @router.get("/")
 async def get_all_playlists(  # noqa: PLR0913
     current_user: Annotated[User, Depends(get_current_active_user_flexible)],  # noqa: ARG001
@@ -72,30 +79,46 @@ async def get_all_playlists(  # noqa: PLR0913
 async def get_user_playlists(
     current_user: Annotated[User, Depends(get_current_active_user_flexible)],
     playlist_service: Annotated[PlaylistService, Depends(get_playlist_service)],
+    favorite_service: Annotated[FavoriteService, Depends(get_favorite_service)],
 ) -> list[PlaylistResponse]:
     """Get playlists for the current user only."""
     playlists = await playlist_service.get_user_playlists(current_user.id)
-    return [PlaylistResponse.from_playlist(playlist) for playlist in playlists]
+    
+    # Add favorite indicators for each playlist
+    playlist_responses = []
+    for playlist in playlists:
+        is_favorited = await favorite_service.is_playlist_favorited(current_user.id, playlist.id)
+        favorite_count = await favorite_service.get_playlist_favorite_count(playlist.id)
+        playlist_response = PlaylistResponse.from_playlist(playlist, is_favorited, favorite_count)
+        playlist_responses.append(playlist_response)
+    
+    return playlist_responses
 
 
 @router.get("/main")
 async def get_main_playlist(
-    current_user: Annotated[User, Depends(get_current_active_user_flexible)],  # noqa: ARG001
+    current_user: Annotated[User, Depends(get_current_active_user_flexible)],
     playlist_service: Annotated[PlaylistService, Depends(get_playlist_service)],
+    favorite_service: Annotated[FavoriteService, Depends(get_favorite_service)],
 ) -> PlaylistResponse:
     """Get the global main playlist."""
     playlist = await playlist_service.get_main_playlist()
-    return PlaylistResponse.from_playlist(playlist)
+    is_favorited = await favorite_service.is_playlist_favorited(current_user.id, playlist.id)
+    favorite_count = await favorite_service.get_playlist_favorite_count(playlist.id)
+    return PlaylistResponse.from_playlist(playlist, is_favorited, favorite_count)
 
 
 @router.get("/current")
 async def get_current_playlist(
-    current_user: Annotated[User, Depends(get_current_active_user_flexible)],  # noqa: ARG001
+    current_user: Annotated[User, Depends(get_current_active_user_flexible)],
     playlist_service: Annotated[PlaylistService, Depends(get_playlist_service)],
+    favorite_service: Annotated[FavoriteService, Depends(get_favorite_service)],
 ) -> PlaylistResponse:
     """Get the global current playlist (falls back to main playlist)."""
     playlist = await playlist_service.get_current_playlist()
-    return PlaylistResponse.from_playlist(playlist)
+    is_favorited = await favorite_service.is_playlist_favorited(current_user.id, playlist.id)
+    favorite_count = await favorite_service.get_playlist_favorite_count(playlist.id)
+    return PlaylistResponse.from_playlist(playlist, is_favorited, favorite_count)
 
 
 @router.post("/")
@@ -117,12 +140,15 @@ async def create_playlist(
 @router.get("/{playlist_id}")
 async def get_playlist(
     playlist_id: int,
-    current_user: Annotated[User, Depends(get_current_active_user_flexible)],  # noqa: ARG001
+    current_user: Annotated[User, Depends(get_current_active_user_flexible)],
     playlist_service: Annotated[PlaylistService, Depends(get_playlist_service)],
+    favorite_service: Annotated[FavoriteService, Depends(get_favorite_service)],
 ) -> PlaylistResponse:
     """Get a specific playlist."""
     playlist = await playlist_service.get_playlist_by_id(playlist_id)
-    return PlaylistResponse.from_playlist(playlist)
+    is_favorited = await favorite_service.is_playlist_favorited(current_user.id, playlist.id)
+    favorite_count = await favorite_service.get_playlist_favorite_count(playlist.id)
+    return PlaylistResponse.from_playlist(playlist, is_favorited, favorite_count)
 
 
 @router.put("/{playlist_id}")