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/Persisence/DataController.swift

@@ -7,9 +7,11 @@
 
 import SwiftData
 import SwiftUI
+import os.log
 
 @MainActor
 final class DataController: ObservableObject {
+    private static let logger = Logger(subsystem: Bundle.main.bundleIdentifier ?? "com.tt.ifeel", category: "DataController")
     static let shared = DataController()
 
     private(set) var container: ModelContainer
@@ -45,14 +47,14 @@ final class DataController: ObservableObject {
 
     private init() {
         let cloudKit = GroupUserDefaults.groupDefaults.bool(forKey: UserDefaultsStore.Keys.useCloudKit.rawValue)
-        container = SharedModelContainer.create(useCloudKit: cloudKit)
+        container = SharedModelContainer.createWithFallback(useCloudKit: cloudKit)
     }
 
     // MARK: - Container Switching (for CloudKit toggle)
 
     func switchContainer() {
         save()
-        container = SharedModelContainer.create(useCloudKit: useCloudKit)
+        container = SharedModelContainer.createWithFallback(useCloudKit: useCloudKit)
         for listener in switchContainerListeners {
             listener()
         }
@@ -76,7 +78,7 @@ final class DataController: ObservableObject {
         do {
             try modelContext.save()
         } catch {
-            print("Failed to save context: \(error)")
+            Self.logger.error("Failed to save context: \(error.localizedDescription)")
         }
     }
 }