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/FoilEngine.swift

@@ -0,0 +1,48 @@
+import Vision
+import CoreML
+import CoreGraphics
+
+// MARK: - FOIL ENGINE
+actor FoilEngine {
+    private var frameCounter = 0
+    private var lowConfidenceStreak = 0
+
+    static var model: VNCoreMLModel? = {
+        guard AppConfig.enableFoilDetection else { return nil }
+        return ModelManager.shared.getModel(name: "IYmtgFoilClassifier")
+    }()
+
+    private lazy var request: VNCoreMLRequest? = {
+        guard let model = FoilEngine.model else { return nil }
+        let req = VNCoreMLRequest(model: model)
+        req.imageCropAndScaleOption = .scaleFill
+        return req
+    }()
+
+    func addFrame(_ image: CGImage, orientation: CGImagePropertyOrientation = .up) -> String? {
+        frameCounter += 1
+        // SAFETY: Prevent integer overflow in long-running sessions
+        if frameCounter > 1000 { frameCounter = 0 }
+        if frameCounter % 5 != 0 { return nil }
+        guard let request = self.request else { return AppConfig.Defaults.defaultFoil }
+
+        let handler = VNImageRequestHandler(cgImage: image, orientation: orientation, options: [:])
+
+        do {
+            try handler.perform([request])
+            guard let results = request.results as? [VNClassificationObservation], let top = results.first else { return AppConfig.Defaults.defaultFoil }
+
+            if top.confidence > 0.85 {
+                lowConfidenceStreak = 0
+                return top.identifier
+            } else {
+                lowConfidenceStreak += 1
+                if lowConfidenceStreak >= 3 {
+                    return AppConfig.Defaults.defaultFoil
+                } else {
+                    return nil
+                }
+            }
+        } catch { return AppConfig.Defaults.defaultFoil }
+    }
+}