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/core/config.py

@@ -30,9 +30,7 @@ class Settings(BaseSettings):
     LOG_FORMAT: str = "%(asctime)s - %(name)s - %(levelname)s - %(message)s"
 
     # JWT Configuration
-    JWT_SECRET_KEY: str = (
-        "your-secret-key-change-in-production"  # noqa: S105 default value if none set in .env
-    )
+    JWT_SECRET_KEY: str = "your-secret-key-change-in-production"  # noqa: S105 default value if none set in .env
     JWT_ALGORITHM: str = "HS256"
     JWT_ACCESS_TOKEN_EXPIRE_MINUTES: int = 15
     JWT_REFRESH_TOKEN_EXPIRE_DAYS: int = 7