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/YearView/YearView.swift

@@ -26,6 +26,7 @@ struct YearView: View {
 
     /// Cached sorted year keys to avoid re-sorting in ForEach on every render
     @State private var cachedSortedYearKeys: [Int] = []
+    @State private var cachedDemoYearData: [Int: [Int: [DayChartView]]] = [:]
 
     // MARK: - Demo Animation
     @StateObject private var demoManager = DemoAnimationManager.shared
@@ -34,7 +35,7 @@ struct YearView: View {
     private let heatmapColumns = Array(repeating: GridItem(.flexible(), spacing: 2), count: 12)
 
     /// Generate demo year data for the past 3 years (full 12 months each)
-    private var demoYearData: [Int: [Int: [DayChartView]]] {
+    private func computeDemoYearData() -> [Int: [Int: [DayChartView]]] {
         var result: [Int: [Int: [DayChartView]]] = [:]
         let calendar = Calendar.current
         let currentYear = calendar.component(.year, from: Date())
@@ -107,7 +108,7 @@ struct YearView: View {
     /// Year keys to display - demo data or real data
     private var displayYearKeys: [Int] {
         if demoManager.isDemoMode {
-            return Array(demoYearData.keys.sorted(by: >))
+            return Array(cachedDemoYearData.keys.sorted(by: >))
         }
         return cachedSortedYearKeys
     }
@@ -115,7 +116,7 @@ struct YearView: View {
     /// Year data for a specific year - demo or real
     private func yearDataFor(_ year: Int) -> [Int: [DayChartView]] {
         if demoManager.isDemoMode {
-            return demoYearData[year] ?? [:]
+            return cachedDemoYearData[year] ?? [:]
         }
         return viewModel.data[year] ?? [:]
     }
@@ -282,7 +283,7 @@ struct YearView: View {
         .onAppear(perform: {
             self.viewModel.filterEntries(startDate: Date(timeIntervalSince1970: 0), endDate: Date())
             cachedSortedYearKeys = Array(viewModel.data.keys.sorted(by: >))
-            // Demo mode is toggled manually via triple-tap
+            cachedDemoYearData = computeDemoYearData()
         })
         .onChange(of: viewModel.data.keys.count) { _, _ in
             cachedSortedYearKeys = Array(viewModel.data.keys.sorted(by: >))
@@ -787,6 +788,19 @@ struct DemoYearHeatmapCell: View {
             // Generate random mood once when cell appears
             randomMood = DemoAnimationManager.randomPositiveMood()
         }
+        .accessibilityLabel(accessibilityDescription)
+    }
+
+    private var accessibilityDescription: String {
+        if !isFiltered {
+            return "Filtered out"
+        } else if color == Mood.placeholder.color {
+            return "Empty"
+        } else if color == Mood.missing.color {
+            return "No mood logged"
+        } else {
+            return "Mood entry"
+        }
     }
 
     /// Whether this cell has been animated (filled with color)

Shared/Views/YearView/YearViewModel.swift

@@ -24,13 +24,23 @@ class YearViewModel: ObservableObject {
         }
     }
 
+    private var dataListenerToken: DataController.DataListenerToken?
+
     init() {
-        DataController.shared.addNewDataListener { [weak self] in
+        dataListenerToken = DataController.shared.addNewDataListener { [weak self] in
             self?.refreshData()
         }
         updateData()
     }
 
+    deinit {
+        if let token = dataListenerToken {
+            Task { @MainActor in
+                DataController.shared.removeDataListener(token: token)
+            }
+        }
+    }
+
     /// Re-fetch data using the current date range. Called by the data listener
     /// when mood entries change in other tabs.
     public func refreshData() {