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/Core/Services/DeepLinkHandler.swift

@@ -8,6 +8,13 @@
 import Foundation
 import SwiftUI
 
+// MARK: - Identifiable Share Code
+
+struct IdentifiableShareCode: Identifiable {
+    let id: String
+    var value: String { id }
+}
+
 // MARK: - Deep Link Handler
 
 @MainActor
@@ -19,7 +26,7 @@ final class DeepLinkHandler {
 
     /// The pending poll share code from a deep link
     /// Setting to nil clears the pending state
-    var pendingPollShareCode: String? {
+    var pendingPollShareCode: IdentifiableShareCode? {
         didSet {
             if pendingPollShareCode == nil {
                 pendingPoll = nil
@@ -49,7 +56,7 @@ final class DeepLinkHandler {
 
         switch destination {
         case .poll(let shareCode):
-            pendingPollShareCode = shareCode
+            pendingPollShareCode = IdentifiableShareCode(id: shareCode)
         }
 
         return destination