fix(data): populate stadium timezone in scrapers and CloudKit sync

Stadium timezones were always null because scrapers weren't passing
the timezone from STADIUM_MAPPINGS to the Stadium constructor. This
fix propagates timezone data through the entire pipeline: scrapers,
CloudKit uploader, and Swift CloudKit model.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Scripts/sportstime_parser/uploaders/diff.py

@@ -545,6 +545,7 @@ class RecordDiffer:
         - yearOpened: Year opened as int
         - imageURL: URL string for stadium image
         - sport: Sport code uppercase (e.g., "MLB")
+        - timezoneIdentifier: IANA timezone (e.g., "America/New_York")
         """
         return CloudKitRecord(
             record_name=stadium.id,
@@ -564,6 +565,7 @@ class RecordDiffer:
                 "capacity": stadium.capacity,
                 "yearOpened": stadium.opened_year,
                 "imageURL": stadium.image_url,
+                "timezoneIdentifier": stadium.timezone,
             },
         )