Migrate from Core Data to SwiftData

- Replace Core Data with SwiftData for iOS 18+
- Create MoodEntryModel as @Model class replacing MoodEntry entity
- Create SharedModelContainer for App Group container sharing
- Create DataController with CRUD extensions replacing PersistenceController
- Update all views and view models to use MoodEntryModel
- Update widget extension to use SwiftData
- Remove old Core Data files (Persistence*.swift, .xcdatamodeld)
- Add EntryType enum with all entry type cases
- Fix widget label truncation with proper spacing and text scaling

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

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

Shared/BGTask.swift

@@ -10,15 +10,16 @@ import BackgroundTasks
 
 class BGTask {
     static let updateDBMissingID = "com.tt.ifeel.dbUpdateMissing"
-    
+
+    @MainActor
     class func runFillInMissingDatesTask(task: BGProcessingTask) {
         BGTask.scheduleBackgroundProcessing()
-        
+
         task.expirationHandler = {
             task.setTaskCompleted(success: false)
         }
-        
-        PersistenceController.shared.fillInMissingDates()
+
+        DataController.shared.fillInMissingDates()
         task.setTaskCompleted(success: true)
     }