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/Settings/Views/SettingsView.swift

@@ -229,6 +229,9 @@ struct SettingsView: View {
                         .accessibilityHidden(true)
                 }
             }
+            .accessibilityLabel("Animated background")
+            .accessibilityValue(DesignStyleManager.shared.animationsEnabled ? "On" : "Off")
+            .accessibilityHint("Toggle animated sports graphics on home screen")
             .accessibilityIdentifier("settings.animationsToggle")
         } header: {
             Text("Home Screen")