fix: 13 audit fixes — memory, concurrency, performance, accessibility

Critical:
- ProgressViewModel: use single stored ModelContext instead of creating
  new ones per operation (deleteVisit silently no-op'd)
- ProgressViewModel: convert expensive computed properties to stored
  with explicit recompute after mutations (3x recomputation per render)

Memory:
- AnimatedSportsIcon: replace recursive GCD asyncAfter with Task loop,
  cancelled in onDisappear (19 unkillable timer chains)
- ItineraryItemService: remove [weak self] from actor Task (semantically
  wrong, silently drops flushPendingUpdates)
- VisitPhotoService: remove [weak self] from @MainActor Task closures

Concurrency:
- StoreManager: replace nested MainActor.run{Task{}} with direct await
  in listenForTransactions (fire-and-forget race)
- VisitPhotoService: move JPEG encoding/file writing off MainActor via
  nonisolated static helper + Task.detached
- SportsIconImageGenerator: replace GCD dispatch with Task.detached for
  structured concurrency compliance

Performance:
- Game/RichGame: cache DateFormatters as static lets instead of
  allocating per-call (hundreds of allocations in schedule view)
- TripDetailView: wrap ~10 routeWaypoints print() in #if DEBUG, remove
  2 let _ = print() from TripMapView.body (fires every render)

Accessibility:
- GameRow: add combined VoiceOver label (was reading abbreviations
  letter-by-letter)
- Sport badges: add accessibilityLabel to prevent SF symbol name readout
- SportsTimeApp: post UIAccessibility.screenChanged after bootstrap
  completes so VoiceOver users know app is ready

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

SportsTime/SportsTimeApp.swift

@@ -250,6 +250,7 @@ struct BootstrappedContentView: View {
             // 8. App is now usable
             print("🚀 [BOOT] Step 8: Bootstrap complete - app ready")
             isBootstrapping = false
+            UIAccessibility.post(notification: .screenChanged, argument: nil)
 
             // 9-10: Background sync (skip in UI test mode)
             if !ProcessInfo.isUITesting {