fix: 14 audit fixes — concurrency, memory, performance, accessibility

Second audit round addressing data races, task stacking, unbounded
caches, and VoiceOver gaps across 7 files.

Concurrency:
- Move NSItemProvider @State access into MainActor block (3 drop handlers)
- Cancel stale ScheduleViewModel tasks on rapid filter changes

Memory:
- Replace unbounded image dict with LRUCache(countLimit: 50)
- Replace demo-mode asyncAfter with cancellable Task

Performance:
- Wrap debug NBA print() in #if DEBUG
- Cache visitsById via @State + onChange instead of per-render computed
- Pre-compute sportProgressFractions in ProgressViewModel
- Replace allGames computed property with hasGames bool check
- Cache sortedTrips via @State + onChange in SavedTripsListView

Accessibility:
- Add combined VoiceOver label to progress ring
- Combine away/home team text into single readable phrase
- Hide decorative StadiumDetailSheet icon from VoiceOver
- Add explicit accessibilityLabel to SportFilterChip
- Add combined accessibilityLabel to GameRowView

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

SportsTime/Features/Schedule/Views/ScheduleListView.swift

@@ -11,17 +11,17 @@ struct ScheduleListView: View {
     @State private var showDatePicker = false
     @State private var showDiagnostics = false
 
-    private var allGames: [RichGame] {
-        viewModel.gamesBySport.flatMap(\.games)
+    private var hasGames: Bool {
+        !viewModel.gamesBySport.isEmpty
     }
 
     var body: some View {
         Group {
-            if viewModel.isLoading && allGames.isEmpty {
+            if viewModel.isLoading && !hasGames {
                 loadingView
             } else if let errorMessage = viewModel.errorMessage {
                 errorView(message: errorMessage)
-            } else if allGames.isEmpty {
+            } else if !hasGames {
                 emptyView
             } else {
                 gamesList
@@ -224,6 +224,7 @@ struct SportFilterChip: View {
         }
         .buttonStyle(.plain)
         .accessibilityIdentifier("schedule.sport.\(sport.rawValue.lowercased())")
+        .accessibilityLabel(sport.rawValue)
         .accessibilityValue(isSelected ? "Selected" : "Not selected")
         .accessibilityAddTraits(isSelected ? .isSelected : [])
     }
@@ -313,6 +314,18 @@ struct GameRowView: View {
         }
         .padding(.vertical, 4)
         .listRowBackground(isToday ? Color.orange.opacity(0.1) : nil)
+        .accessibilityElement(children: .ignore)
+        .accessibilityLabel(gameAccessibilityLabel)
+    }
+
+    private var gameAccessibilityLabel: String {
+        var parts = ["\(game.awayTeam.name) at \(game.homeTeam.name)"]
+        parts.append(game.stadium.name)
+        parts.append(game.localGameTimeShort)
+        if showDate {
+            parts.append(Self.dateFormatter.string(from: game.game.dateTime))
+        }
+        return parts.joined(separator: ", ")
     }
 }