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/Persisence/SharedModelContainer.swift

@@ -0,0 +1,79 @@
+//
+//  SharedModelContainer.swift
+//  Feels
+//
+//  Factory for creating ModelContainer shared between main app and widget extension.
+//
+
+import Foundation
+import SwiftData
+
+enum SharedModelContainer {
+    /// Creates a ModelContainer with the appropriate configuration for app group sharing
+    /// - Parameter useCloudKit: Whether to enable CloudKit sync
+    /// - Returns: Configured ModelContainer
+    static func create(useCloudKit: Bool = false) -> ModelContainer {
+        let schema = Schema([MoodEntryModel.self])
+        let storeURL = Self.storeURL
+
+        let configuration: ModelConfiguration
+        if useCloudKit {
+            // CloudKit-enabled configuration
+            configuration = ModelConfiguration(
+                schema: schema,
+                url: storeURL,
+                cloudKitDatabase: .private(cloudKitContainerID)
+            )
+        } else {
+            // Local-only configuration
+            configuration = ModelConfiguration(
+                schema: schema,
+                url: storeURL,
+                cloudKitDatabase: .none
+            )
+        }
+
+        do {
+            return try ModelContainer(for: schema, configurations: [configuration])
+        } catch {
+            fatalError("Failed to create ModelContainer: \(error)")
+        }
+    }
+
+    /// The URL for the SwiftData store in the shared app group container
+    static var storeURL: URL {
+        guard let containerURL = FileManager.default.containerURL(
+            forSecurityApplicationGroupIdentifier: appGroupID
+        ) else {
+            fatalError("App Group container not available for: \(appGroupID)")
+        }
+        return containerURL.appendingPathComponent(storeFileName)
+    }
+
+    /// App Group identifier based on build configuration
+    static var appGroupID: String {
+        #if DEBUG
+        return Constants.groupShareIdDebug
+        #else
+        return Constants.groupShareId
+        #endif
+    }
+
+    /// CloudKit container identifier based on build configuration
+    static var cloudKitContainerID: String {
+        #if DEBUG
+        return "iCloud.com.tt.ifeelDebug"
+        #else
+        return "iCloud.com.tt.ifeel"
+        #endif
+    }
+
+    /// Store file name based on build configuration
+    static var storeFileName: String {
+        #if DEBUG
+        return "Feels-Debug.store"
+        #else
+        return "Feels.store"
+        #endif
+    }
+}