Fix 25 audit issues: memory leaks, concurrency, performance, accessibility

Address findings from comprehensive audit across 5 workstreams:

- Memory: Token-based DataController listeners (prevent closure leaks),
  static DateFormatters, ImageCache observer cleanup, MotionManager
  reference counting, FoundationModels dedup guard
- Concurrency: Replace Task.detached with Task in FeelsApp (preserve
  MainActor isolation), wrap WatchConnectivity handler in MainActor
- Performance: Cache sortedGroupedData in DayViewViewModel, cache demo
  data in MonthView/YearView, remove broken ReduceMotionModifier
- Accessibility: VoiceOver support for LockScreen, DemoHeatmapCell
  labels, MonthCard button labels, InsightsView header traits,
  Smart Invert protection on neon headers

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

Shared/Views/MonthView/MonthView.swift

@@ -44,12 +44,13 @@ struct MonthView: View {
 
     /// Cached sorted year/month data to avoid recalculating in ForEach
     @State private var cachedSortedData: [(year: Int, months: [(month: Int, entries: [MoodEntryModel])])] = []
+    @State private var cachedDemoSortedData: [(year: Int, months: [(month: Int, entries: [MoodEntryModel])])] = []
 
     // MARK: - Demo Animation
     @StateObject private var demoManager = DemoAnimationManager.shared
 
     /// Generate fake demo data for the past 12 months
-    private var demoSortedData: [(year: Int, months: [(month: Int, entries: [MoodEntryModel])])] {
+    private func computeDemoSortedData() -> [(year: Int, months: [(month: Int, entries: [MoodEntryModel])])] {
         var result: [(year: Int, months: [(month: Int, entries: [MoodEntryModel])])] = []
         let calendar = Calendar.current
         let now = Date()
@@ -158,7 +159,7 @@ struct MonthView: View {
 
     /// Data to display - uses demo data when in demo mode, otherwise cached real data
     private var displayData: [(year: Int, months: [(month: Int, entries: [MoodEntryModel])])] {
-        demoManager.isDemoMode ? demoSortedData : cachedSortedData
+        demoManager.isDemoMode ? cachedDemoSortedData : cachedSortedData
     }
 
     var body: some View {
@@ -362,7 +363,7 @@ struct MonthView: View {
         }
         .onAppear {
             cachedSortedData = computeSortedYearMonthData()
-            // Demo mode is toggled manually via triple-tap
+            cachedDemoSortedData = computeDemoSortedData()
         }
         .onChange(of: viewModel.numberOfItems) { _, _ in
             // Use numberOfItems as a lightweight proxy for data changes
@@ -588,6 +589,8 @@ struct MonthCard: View, Equatable {
                     }
                 }
                 .buttonStyle(.plain)
+                .accessibilityLabel("\(Random.monthName(fromMonthInt: month)) \(String(year)), \(showStats ? "expanded" : "collapsed")")
+                .accessibilityHint("Double tap to toggle statistics")
 
                 Spacer()
 
@@ -599,6 +602,7 @@ struct MonthCard: View, Equatable {
                         .foregroundColor(labelColor.opacity(0.6))
                 }
                 .buttonStyle(.plain)
+                .accessibilityLabel("Share \(Random.monthName(fromMonthInt: month)) \(String(year)) mood data")
             }
             .padding(.horizontal, 16)
             .padding(.vertical, 12)
@@ -753,6 +757,7 @@ struct DemoHeatmapCell: View {
             // Generate random mood once when cell appears
             randomMood = DemoAnimationManager.randomPositiveMood()
         }
+        .accessibilityLabel(accessibilityDescription)
     }
 
     /// Whether this cell has been animated (filled with color)
@@ -784,6 +789,18 @@ struct DemoHeatmapCell: View {
             return moodTint.color(forMood: entry.mood)
         }
     }
+
+    private var accessibilityDescription: String {
+        if entry.mood == .placeholder {
+            return "Empty day"
+        } else if entry.mood == .missing {
+            return "No mood logged for \(DateFormattingCache.shared.string(for: entry.forDate, format: .dateMedium))"
+        } else if !isFiltered {
+            return "\(DateFormattingCache.shared.string(for: entry.forDate, format: .dateMedium)): \(entry.mood.strValue) (filtered out)"
+        } else {
+            return "\(DateFormattingCache.shared.string(for: entry.forDate, format: .dateMedium)): \(entry.mood.strValue)"
+        }
+    }
 }
 
 // MARK: - Mini Bar Chart