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/Views/AddMoodHeaderView.swift

@@ -7,7 +7,7 @@
 
 import Foundation
 import SwiftUI
-import CoreData
+import SwiftData
 
 struct AddMoodHeaderView: View {
     @AppStorage(UserDefaultsStore.Keys.theme.rawValue, store: GroupUserDefaults.groupDefaults) private var theme: Theme = .system
@@ -255,11 +255,11 @@ struct AddMoodHeaderView_Previews: PreviewProvider {
         Group {
             AddMoodHeaderView(addItemHeaderClosure: { (_,_) in
 
-            }).environment(\.managedObjectContext, PersistenceController.shared.viewContext)
+            }).modelContainer(DataController.shared.container)
 
             AddMoodHeaderView(addItemHeaderClosure: { (_,_) in
 
-            }).preferredColorScheme(.dark).environment(\.managedObjectContext, PersistenceController.shared.viewContext)
+            }).preferredColorScheme(.dark).modelContainer(DataController.shared.container)
         }
     }
 }