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/DayView/DayView.swift

@@ -95,11 +95,9 @@ struct DayView: View {
         }
     }
 
-    /// Cached sorted year/month data to avoid sorting dictionaries in ForEach
+    /// Sorted year/month data cached in ViewModel — avoids re-sorting on every render
     private var sortedGroupedData: [(year: Int, months: [(month: Int, entries: [MoodEntryModel])])] {
-        viewModel.grouped
-            .sorted { $0.key > $1.key }
-            .map { (year: $0.key, months: $0.value.sorted { $0.key > $1.key }.map { (month: $0.key, entries: $0.value) }) }
+        viewModel.sortedGroupedData
     }
 
     private var listView: some View {
@@ -313,6 +311,7 @@ extension DayView {
                 }
             }
         )
+        .accessibilityIgnoresInvertColors(true)
     }
 
     private func inkSectionHeader(month: Int, year: Int) -> some View {