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/BackgroundSyncManager.swift

@@ -84,7 +84,9 @@ final class BackgroundSyncManager {
             }
         }
 
+        #if DEBUG
         print("Background tasks registered")
+        #endif
     }
 
     // MARK: - Task Scheduling
@@ -100,9 +102,13 @@ final class BackgroundSyncManager {
 
         do {
             try BGTaskScheduler.shared.submit(request)
+            #if DEBUG
             print("Background refresh scheduled")
+            #endif
         } catch {
+            #if DEBUG
             print("Failed to schedule background refresh: \(error.localizedDescription)")
+            #endif
         }
     }
 
@@ -129,9 +135,13 @@ final class BackgroundSyncManager {
 
         do {
             try BGTaskScheduler.shared.submit(request)
+            #if DEBUG
             print("Overnight processing task scheduled for \(targetDate)")
+            #endif
         } catch {
+            #if DEBUG
             print("Failed to schedule processing task: \(error.localizedDescription)")
+            #endif
         }
     }
 
@@ -519,11 +529,15 @@ final class BackgroundSyncManager {
             }
 
             try context.save()
+            #if DEBUG
             print("Background cleanup: Archived \(oldGames.count) old games")
+            #endif
             return true
 
         } catch {
+            #if DEBUG
             print("Background cleanup failed: \(error.localizedDescription)")
+            #endif
             return false
         }
     }