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/Schedule/ViewModels/ScheduleViewModel.swift

@@ -28,7 +28,7 @@ final class ScheduleViewModel {
     private(set) var errorMessage: String?
 
     private let dataProvider = AppDataProvider.shared
-    private var loadTask: Task<Void, Never>?
+    nonisolated(unsafe) private var loadTask: Task<Void, Never>?
 
     // MARK: - Pre-computed Groupings (avoid computed property overhead)
 
@@ -43,6 +43,10 @@ final class ScheduleViewModel {
     /// Debug info for troubleshooting missing games
     private(set) var diagnostics: ScheduleDiagnostics = ScheduleDiagnostics()
 
+    deinit {
+        loadTask?.cancel()
+    }
+
     var hasFilters: Bool {
         selectedSports.count < Sport.supported.count || !searchText.isEmpty
     }