Add comprehensive tests for playlist service and refactor socket service tests

- Introduced a new test suite for the PlaylistService covering various functionalities including creation, retrieval, updating, and deletion of playlists.
- Added tests for handling sounds within playlists, ensuring correct behavior when adding/removing sounds and managing current playlists.
- Refactored socket service tests for improved readability by adjusting function signatures.
- Cleaned up unnecessary whitespace in sound normalizer and sound scanner tests for consistency.
- Enhanced audio utility tests to ensure accurate hash and size calculations, including edge cases for nonexistent files.
- Removed redundant blank lines in cookie utility tests for cleaner code.

app/repositories/sound.py

@@ -116,11 +116,7 @@ class SoundRepository:
     async def get_popular_sounds(self, limit: int = 10) -> list[Sound]:
         """Get the most played sounds."""
         try:
-            statement = (
-                select(Sound)
-                .order_by(desc(Sound.play_count))
-                .limit(limit)
-            )
+            statement = select(Sound).order_by(desc(Sound.play_count)).limit(limit)
             result = await self.session.exec(statement)
             return list(result.all())
         except Exception:
@@ -147,5 +143,7 @@ class SoundRepository:
             result = await self.session.exec(statement)
             return list(result.all())
         except Exception:
-            logger.exception("Failed to get unnormalized sounds by type: %s", sound_type)
+            logger.exception(
+                "Failed to get unnormalized sounds by type: %s", sound_type
+            )
             raise