Added year_opened field to stadium data across all 4 sport modules:
- MLB: 30 ballparks (1912-2023)
- NBA: 30 arenas (1968-2024)
- NHL: 32 arenas (1968-2021)
- NFL: 30 stadiums (1924-2020)
Updated Stadium object creation in all modules to pass year_opened.
Stadium dataclass already supported the field.
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
Extract NFL scrapers from monolithic scrape_schedules.py into dedicated
sport module following established pattern from nba.py/nhl.py:
- NFL_TEAMS: 32 teams with stadiums
- Game scrapers: ESPN API, Pro-Football-Reference, CBS Sports
- Stadium scrapers: ScoreBot, GeoJSON gist, hardcoded fallback
- NFL_GAME_SOURCES and NFL_STADIUM_SOURCES configurations
- get_nfl_season_string() for cross-calendar-year format (2025-26)
- scrape_nfl_games() convenience function with fallback
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
