* feat(nhl): Integrate NHL manager with background service
- Fix NHL data source to use ESPN API instead of NHL.com API
- Add background service integration following NFL/NCAA pattern
- Add HTTP session with retry strategy and proper headers
- Add background fetch request tracking and callback handling
- Add synchronous fallback when background service disabled
- Update _fetch_nhl_api_data() to use background threading
- Simplify _fetch_data() method for consistency
- Add _fetch_nhl_api_data_sync() for direct API fallback
This brings NHL manager in line with other sports managers and resolves
the 'No events found in ESPN API response' error by using the correct
ESPN API endpoint that matches the existing parsing logic.
* update NHL
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