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/CoreML/ModelManager.swift

@@ -0,0 +1,75 @@
+import CoreML
+import Vision
+import FirebaseStorage
+
+struct SharedEngineResources {
+    static let context = CIContext()
+}
+
+// MARK: - MODEL MANAGER (OTA Updates)
+class ModelManager {
+    static let shared = ModelManager()
+    private let defaults = UserDefaults.standard
+
+    func getModel(name: String) -> VNCoreMLModel? {
+        // 1. Check Documents (Downloaded Update)
+        if let docDir = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first {
+            let modelURL = docDir.appendingPathComponent("models/\(name).mlmodelc")
+            if FileManager.default.fileExists(atPath: modelURL.path),
+               let model = try? MLModel(contentsOf: modelURL),
+               let vnModel = try? VNCoreMLModel(for: model) {
+                return vnModel
+            }
+        }
+
+        // 2. Check Bundle (Built-in Fallback)
+        if let bundleURL = Bundle.main.url(forResource: name, withExtension: "mlmodelc"),
+           let model = try? MLModel(contentsOf: bundleURL),
+           let vnModel = try? VNCoreMLModel(for: model) {
+            return vnModel
+        }
+        return nil
+    }
+
+    func checkForUpdates() {
+        guard FirebaseApp.app() != nil else { return }
+        let models = ["IYmtgFoilClassifier", "IYmtgConditionClassifier", "IYmtgStampClassifier", "IYmtgSetClassifier"]
+
+        for name in models {
+            let ref = Storage.storage().reference().child("models/\(name).mlmodel")
+            ref.getMetadata { meta, error in
+                guard let meta = meta, let remoteDate = meta.updated else { return }
+                let localDate = self.defaults.object(forKey: "ModelDate_\(name)") as? Date ?? Date.distantPast
+
+                if remoteDate > localDate {
+                    let tempURL = FileManager.default.temporaryDirectory.appendingPathComponent("\(name).mlmodel")
+                    ref.write(toFile: tempURL) { url, error in
+                        guard let url = url else { return }
+                        DispatchQueue.global(qos: .utility).async {
+                            do {
+                                let compiledURL = try MLModel.compileModel(at: url)
+                                let docDir = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask)[0].appendingPathComponent("models")
+                                try FileManager.default.createDirectory(at: docDir, withIntermediateDirectories: true)
+                                let destURL = docDir.appendingPathComponent("\(name).mlmodelc")
+                                let tempDestURL = docDir.appendingPathComponent("temp_\(name).mlmodelc")
+
+                                try? FileManager.default.removeItem(at: tempDestURL)
+                                try FileManager.default.copyItem(at: compiledURL, to: tempDestURL)
+
+                                if FileManager.default.fileExists(atPath: destURL.path) {
+                                    _ = try FileManager.default.replaceItem(at: destURL, withItemAt: tempDestURL, backupItemName: nil, options: [])
+                                } else {
+                                    try FileManager.default.moveItem(at: tempDestURL, to: destURL)
+                                }
+                                self.defaults.set(remoteDate, forKey: "ModelDate_\(name)")
+                                print("✅ OTA Model Updated: \(name)")
+                            } catch {
+                                print("❌ Model Update Failed for \(name): \(error)")
+                            }
+                        }
+                    }
+                }
+            }
+        }
+    }
+}