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/Stats.swift

@@ -8,7 +8,7 @@
 import Foundation
 
 class Stats {
-    static func getCountFor(moodType: Mood, inData data: [MoodEntry]) -> Int {
+    static func getCountFor(moodType: Mood, inData data: [MoodEntryModel]) -> Int {
         let num = data.filter({
             $0.moodValue == moodType.rawValue
         }).count