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.

tests/conftest.py

@@ -335,3 +335,5 @@ async def admin_cookies(admin_user: User) -> dict[str, str]:
     access_token = JWTUtils.create_access_token(token_data)
 
     return {"access_token": access_token}
+
+