Refactor sound and extraction services to include user and timestamp fields

- Updated ExtractionInfo to include user_id, created_at, and updated_at fields.
- Modified ExtractionService to return user and timestamp information in extraction responses.
- Enhanced sound serialization in PlayerState to include extraction URL if available.
- Adjusted PlaylistRepository to load sound extractions when retrieving playlist sounds.
- Added tests for new fields in extraction and sound endpoints, ensuring proper response structure.
- Created new test file endpoints for sound downloads and thumbnail retrievals, including success and error cases.
- Refactored various test cases for consistency and clarity, ensuring proper mocking and assertions.

app/api/v1/admin/sounds.py

@@ -226,5 +226,3 @@ async def normalize_sound_by_id(
             status_code=status.HTTP_500_INTERNAL_SERVER_ERROR,
             detail=f"Failed to normalize sound: {e!s}",
         ) from e
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