Fix game times with UTC data, restructure schedule by date

- Update games_canonical.json to use ISO 8601 UTC timestamps (game_datetime_utc)
- Fix BootstrapService timezone-aware parsing for venue-local fallback
- Fix thread-unsafe shared DateFormatter in RichGame local time display
- Bump SchemaVersion to 4 to force re-bootstrap with correct UTC data
- Restructure schedule view: group by date instead of sport, with sport
  icons on each row and date section headers showing game counts
- Fix schedule row backgrounds using Theme.cardBackground instead of black
- Sort games by UTC time with local-time tiebreaker for same-instant games

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

SportsTime/Core/Models/Domain/Game.swift

@@ -130,15 +130,11 @@ struct RichGame: Identifiable, Hashable, Codable {
 
     /// Game time formatted in the stadium's local timezone with timezone indicator
     var localGameTime: String {
-        let formatter = GameFormatters.localTimeFormatter
-        formatter.timeZone = stadium.timeZone ?? .current
-        return formatter.string(from: game.dateTime)
+        game.dateTime.gameTimeString(in: stadium.timeZone, includeZone: true)
     }
 
     /// Game time formatted in the stadium's local timezone without timezone indicator
     var localGameTimeShort: String {
-        let formatter = GameFormatters.localTimeShortFormatter
-        formatter.timeZone = stadium.timeZone ?? .current
-        return formatter.string(from: game.dateTime)
+        game.dateTime.gameTimeString(in: stadium.timeZone)
     }
 }