fix: revert gameDate to local timezone and update DAG router test timing

The hardening pass incorrectly changed Game.gameDate to use UTC, which
broke timezone-dependent departure date calculations in ScenarioDPlanner.
Also widened the DAG router test's same-day game gap to account for the
new 3-hour game duration in canTransition.

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

SportsTime/Core/Models/Domain/Game.swift

@@ -81,7 +81,7 @@ struct Game: Identifiable, Codable, Hashable {
     }
 
     var gameDate: Date {
-        dateTime.startOfDay(in: TimeZone(identifier: "UTC"))
+        Calendar.current.startOfDay(for: dateTime)
     }
 
     /// Alias for TripPlanningEngine compatibility