fix: 22 audit fixes — concurrency, memory, performance, accessibility

- Move 7 Data(contentsOf:) calls off MainActor via Task.detached (BootstrapService)
- Batch-fetch N+1 queries in sync merge loops (CanonicalSyncService)
- Predicate-based gamesForTeam fetch instead of fetching all games (DataProvider)
- Proper Sendable on RouteInfo with nonisolated(unsafe) polyline (LocationService)
- [weak self] in BGTaskScheduler register closures (BackgroundSyncManager)
- Cache tripDays, routeWaypoints as @State with recompute (TripDetailView)
- Remove unused AnyCancellable, add Task lifecycle management (TripDetailView)
- Cache sportStadiums, recentVisits as stored properties (ProgressViewModel)
- Dynamic Type fonts replacing hardcoded sizes (OnboardingPaywallView)
- Accessibility labels/hints on stadium picker, date picker, map, stats,
  settings toggle, and day cards

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

SportsTime/Core/Services/BackgroundSyncManager.swift

@@ -63,10 +63,10 @@ final class BackgroundSyncManager {
         BGTaskScheduler.shared.register(
             forTaskWithIdentifier: Self.refreshTaskIdentifier,
             using: nil
-        ) { task in
+        ) { [weak self] task in
             guard let task = task as? BGAppRefreshTask else { return }
             Task { @MainActor in
-                await self.handleRefreshTask(task)
+                await self?.handleRefreshTask(task)
             }
         }
 
@@ -74,10 +74,10 @@ final class BackgroundSyncManager {
         BGTaskScheduler.shared.register(
             forTaskWithIdentifier: Self.processingTaskIdentifier,
             using: nil
-        ) { task in
+        ) { [weak self] task in
             guard let task = task as? BGProcessingTask else { return }
             Task { @MainActor in
-                await self.handleProcessingTask(task)
+                await self?.handleProcessingTask(task)
             }
         }