fix: codebase audit fixes — safety, accessibility, and production hygiene

Address 16 issues from external audit:
- Move StoreKit transaction listener ownership to StoreManager singleton with proper deinit
- Remove noisy VoiceOver announcements, add missing accessibility on StatPill and BootstrapLoadingView
- Replace String @retroactive Identifiable with IdentifiableShareCode wrapper
- Add crash guard in AchievementEngine getContributingVisitIds + cache stadium lookups
- Pre-compute GamesHistoryViewModel filtered properties to avoid redundant SwiftUI recomputation
- Remove force-unwraps in ProgressMapView with safe guard-let fallback
- Add diff-based update gating in ItineraryTableViewWrapper to prevent unnecessary reloads
- Replace deprecated UIScreen.main with UIWindowScene lookup
- Add deinit task cancellation in ScheduleViewModel and SuggestedTripsGenerator
- Wrap ~234 unguarded print() calls across 27 files in #if DEBUG

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

SportsTime/Features/Progress/Views/ProgressMapView.swift

@@ -182,10 +182,15 @@ extension ProgressMapView {
         let latitudes = stadiums.map { $0.latitude }
         let longitudes = stadiums.map { $0.longitude }
 
-        let minLat = latitudes.min()!
-        let maxLat = latitudes.max()!
-        let minLon = longitudes.min()!
-        let maxLon = longitudes.max()!
+        guard let minLat = latitudes.min(),
+              let maxLat = latitudes.max(),
+              let minLon = longitudes.min(),
+              let maxLon = longitudes.max() else {
+            return MKCoordinateRegion(
+                center: CLLocationCoordinate2D(latitude: 39.8283, longitude: -98.5795),
+                span: MKCoordinateSpan(latitudeDelta: 50, longitudeDelta: 50)
+            )
+        }
 
         let center = CLLocationCoordinate2D(
             latitude: (minLat + maxLat) / 2,