Fix build errors, resolve all warnings, and improve code quality

Widget Extension Fixes:
- Create standalone WidgetDataProvider for widget data isolation
- Add WIDGET_EXTENSION compiler flag for conditional compilation
- Fix DataController references in widget-shared files
- Sync widget version numbers with main app (23, 1.0.2)
- Add WidgetBackground color to asset catalog

Warning Resolutions:
- Fix UIScreen.main deprecation in BGView and SharingListView
- Fix Text '+' concatenation deprecation in PurchaseButtonView and SettingsTabView
- Fix exhaustive switch in BiometricAuthManager (add .none case)
- Fix var to let in ExportService (3 instances)
- Fix unused result warning in NoteEditorView
- Fix ForEach duplicate ID warnings in MonthView and YearView

Code Quality Improvements:
- Wrap bypassSubscription in #if DEBUG for security
- Rename StupidAssCustomWidgetObservableObject to CustomWidgetStateViewModel
- Add @MainActor to IconViewModel
- Replace fatalError with graceful fallback in SharedModelContainer
- Add [weak self] to closures in DayViewViewModel
- Add OSLog-based AppLogger for production logging
- Add ImageCache with NSCache for memory efficiency
- Add AccessibilityHelpers with Reduce Motion support
- Create DataControllerProtocol for dependency injection
- Update .gitignore with secrets exclusions

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Shared/Views/DayView/DayViewViewModel.swift

@@ -35,12 +35,14 @@ class DayViewViewModel: ObservableObject {
     init(addMonthStartWeekdayPadding: Bool) {
         self.addMonthStartWeekdayPadding = addMonthStartWeekdayPadding
 
-        DataController.shared.switchContainerListeners.append {
+        DataController.shared.switchContainerListeners.append { [weak self] in
+            guard let self = self else { return }
             self.getGroupedData(addMonthStartWeekdayPadding: self.addMonthStartWeekdayPadding)
         }
 
-        DataController.shared.addNewDataListener {
-            withAnimation{
+        DataController.shared.addNewDataListener { [weak self] in
+            guard let self = self else { return }
+            withAnimation {
                 self.updateData()
             }
         }