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/api/v1/test_sound_endpoints.py

@@ -870,7 +870,6 @@ class TestSoundEndpoints:
             ) as mock_normalize_sound,
             patch("app.repositories.sound.SoundRepository.get_by_id") as mock_get_sound,
         ):
-
             mock_get_sound.return_value = mock_sound
             mock_normalize_sound.return_value = mock_result
 
@@ -950,7 +949,6 @@ class TestSoundEndpoints:
             ) as mock_normalize_sound,
             patch("app.repositories.sound.SoundRepository.get_by_id") as mock_get_sound,
         ):
-
             mock_get_sound.return_value = mock_sound
             mock_normalize_sound.return_value = mock_result
 
@@ -1003,7 +1001,6 @@ class TestSoundEndpoints:
             ) as mock_normalize_sound,
             patch("app.repositories.sound.SoundRepository.get_by_id") as mock_get_sound,
         ):
-
             mock_get_sound.return_value = mock_sound
             mock_normalize_sound.return_value = mock_result
 
@@ -1059,7 +1056,6 @@ class TestSoundEndpoints:
             ) as mock_normalize_sound,
             patch("app.repositories.sound.SoundRepository.get_by_id") as mock_get_sound,
         ):
-
             mock_get_sound.return_value = mock_sound
             mock_normalize_sound.return_value = mock_result