Implement storage architecture from ai_blueprint.md

Primary sync: replace PersistenceActor JSON file with SwiftData + CloudKit
- Add SavedCardModel (@Model class) and PersistenceController (ModelContainer
  with .automatic CloudKit, fallback to local). BackgroundPersistenceActor
  (@ModelActor) handles all DB I/O off the main thread.
- One-time migration imports user_collection.json into SwiftData and renames
  the original file to prevent re-import.
- Inject modelContainer into SwiftUI environment in IYmtgApp.

Image storage: Documents/UserContent/ subfolder (blueprint requirement)
- ImageManager.dir now targets iCloud Documents/UserContent/ (or local equiv).
- migrateImagesToUserContent() moves existing JPGs to the new subfolder on
  first launch; called during the SwiftData migration.

Firebase: demoted to optional manual backup (metadata only, no images)
- Remove all automatic CloudEngine.save/delete/batchUpdatePrices calls from
  CollectionViewModel mutations.
- Add backupAllToFirebase() for user-triggered metadata sync.
- Add isFirebaseBackupEnabled to AppConfig (default false).
- Add Cloud Backup section in Library settings with iCloud vs Firebase
  explanation and "Backup Metadata to Firebase Now" button.

Also: full modular refactor (Data/, Features/, Services/ directories) and
README updated with CloudKit setup steps and revised release checklist.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

IYmtg_App_iOS/Services/Utilities/DevEngine.swift

@@ -0,0 +1,24 @@
+import Foundation
+import UIKit
+
+// MARK: - SECURE DEV MODE
+class DevEngine {
+    static var isDevMode = false
+
+    static func activateIfCompiled() {
+        #if ENABLE_DEV_MODE
+        isDevMode = true
+        print("⚠️ DEV MODE COMPILED")
+        #endif
+    }
+
+    static func saveRaw(image: UIImage, label: String) {
+        #if ENABLE_DEV_MODE
+        if isDevMode, let data = image.jpegData(compressionQuality: 1.0) {
+            let path = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask)[0].appendingPathComponent("RawTrainingData")
+            try? FileManager.default.createDirectory(at: path, withIntermediateDirectories: true)
+            try? data.write(to: path.appendingPathComponent("TRAIN_\(label)_\(UUID().uuidString).jpg"))
+        }
+        #endif
+    }
+}