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.

tests/services/test_sound_normalizer.py

@@ -182,7 +182,6 @@ class TestSoundNormalizerService:
                 "app.services.sound_normalizer.get_file_hash", return_value="new_hash"
             ),
         ):
-
             # Setup path mocks
             mock_orig_path.return_value = Path("/fake/original.mp3")
             mock_norm_path.return_value = Path("/fake/normalized.mp3")
@@ -256,7 +255,6 @@ class TestSoundNormalizerService:
                 "app.services.sound_normalizer.get_file_hash", return_value="norm_hash"
             ),
         ):
-
             # Setup path mocks
             mock_orig_path.return_value = Path("/fake/original.mp3")
             mock_norm_path.return_value = Path("/fake/normalized.mp3")
@@ -294,7 +292,6 @@ class TestSoundNormalizerService:
             patch.object(normalizer_service, "_get_original_path") as mock_orig_path,
             patch.object(normalizer_service, "_get_normalized_path") as mock_norm_path,
         ):
-
             # Setup path mocks
             mock_orig_path.return_value = Path("/fake/original.mp3")
             mock_norm_path.return_value = Path("/fake/normalized.mp3")
@@ -306,7 +303,6 @@ class TestSoundNormalizerService:
                     normalizer_service, "_normalize_audio_two_pass"
                 ) as mock_normalize,
             ):
-
                 mock_normalize.side_effect = Exception("Normalization failed")
 
                 result = await normalizer_service.normalize_sound(sound)