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/AchievementEngine.swift

@@ -30,6 +30,7 @@ final class AchievementEngine {
 
     private let modelContext: ModelContext
     private let dataProvider: AppDataProvider
+    private var stadiumIdsBySport: [Sport: [String]]?
 
     // MARK: - Initialization
 
@@ -356,6 +357,7 @@ final class AchievementEngine {
         case .visitsInDays(let requiredVisits, let days):
             // Find the qualifying window of visits
             let sortedVisits = visits.sorted { $0.visitDate < $1.visitDate }
+            guard sortedVisits.count >= requiredVisits else { return [] }
             for i in 0...(sortedVisits.count - requiredVisits) {
                 let windowStart = sortedVisits[i].visitDate
                 let windowEnd = sortedVisits[i + requiredVisits - 1].visitDate
@@ -399,15 +401,15 @@ final class AchievementEngine {
     }
 
     private func getStadiumIdsForLeague(_ sport: Sport) -> [String] {
-        // Get all stadium canonical IDs for this sport
-        return dataProvider.stadiums
-            .filter { stadium in
-                // Check if stadium hosts teams of this sport
-                dataProvider.teams.contains { team in
-                    team.stadiumId == stadium.id && team.sport == sport
-                }
+        // Build cache lazily on first access
+        if stadiumIdsBySport == nil {
+            var cache: [Sport: [String]] = [:]
+            for team in dataProvider.teams {
+                cache[team.sport, default: []].append(team.stadiumId)
             }
-            .map { $0.id }
+            stadiumIdsBySport = cache
+        }
+        return stadiumIdsBySport?[sport] ?? []
     }
 
     // MARK: - Data Fetching