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/Features/Progress/Views/ProgressTabView.swift

@@ -247,6 +247,8 @@ struct ProgressTabView: View {
                     label: "Complete"
                 )
             }
+            .accessibilityElement(children: .ignore)
+            .accessibilityLabel("Statistics: \(progress.visitedStadiums) visited, \(progress.totalStadiums - progress.visitedStadiums) remaining, \(String(format: "%.0f", progress.completionPercentage)) percent complete")
         }
         .padding(Theme.Spacing.lg)
         .background(Theme.cardBackground(colorScheme))