feat(02-01): add year_opened to all 122 hardcoded stadiums

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>

.planning/phases/02-stadium-foundation/02-01-SUMMARY.md

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+# Phase 2 Plan 01: Stadium Data Audit & Completion Summary
+
+**Added year_opened field to all 122 hardcoded stadiums across MLB, NBA, NHL, and NFL modules.**
+
+## Accomplishments
+
+- Audited all 4 sport modules confirming expected stadium counts:
+  - MLB: 30 stadiums
+  - NBA: 30 stadiums
+  - NHL: 32 stadiums
+  - NFL: 30 stadiums (includes 2 shared: SoFi Stadium, MetLife Stadium)
+- Verified Stadium dataclass in core.py already has `year_opened: Optional[int] = None`
+- Added year_opened to all hardcoded stadium dictionaries
+- Updated Stadium object creation in all 4 modules to pass year_opened
+
+## Files Modified
+
+- `Scripts/mlb.py` - Added year_opened to 30 ballparks, updated Stadium creation
+- `Scripts/nba.py` - Added year_opened to 30 arenas, updated Stadium creation
+- `Scripts/nhl.py` - Added year_opened to 32 arenas, updated Stadium creation
+- `Scripts/nfl.py` - Added year_opened to 30 stadiums, updated Stadium creation
+
+## Decisions Made
+
+- Used original opening years (not renovation years) for historical accuracy
+- Stadium dataclass already supported year_opened field - no changes needed to core.py
+
+## Issues Encountered
+
+None - all expected stadium counts matched, all fields present.
+
+## Next Step
+
+Ready for 02-02-PLAN.md (pipeline regeneration)