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/Data/Models/Card.swift

@@ -0,0 +1,109 @@
+import Foundation
+
+struct CardFingerprint: Codable, Identifiable, Sendable {
+    let id: UUID
+    let name: String
+    let setCode: String
+    let collectorNumber: String
+    let hasFoilPrinting: Bool
+    let hasSerializedPrinting: Bool?
+    let featureData: Data
+    var priceScanned: Double? = nil
+}
+
+struct CardMetadata: Identifiable, Sendable {
+    let id: UUID
+    let name: String
+    let setCode: String
+    let collectorNumber: String
+    let hasFoilPrinting: Bool
+    let hasSerializedPrinting: Bool
+    var priceScanned: Double? = nil
+    var rarity: String? = nil
+    var colorIdentity: [String]? = nil
+    var isSerialized: Bool = false
+}
+
+struct SavedCard: Codable, Identifiable, Hashable, Sendable {
+    let id: UUID
+    let scryfallID: String
+    var name: String
+    var setCode: String
+    var collectorNumber: String
+    let imageFileName: String
+    var condition: String
+    var foilType: String
+    var currentValuation: Double?
+    var previousValuation: Double?
+    var dateAdded: Date
+    var classification: String
+    var collectionName: String
+    var storageLocation: String
+    var rarity: String?
+    var colorIdentity: [String]?
+
+    // Grading Fields
+    var gradingService: String? // PSA, BGS
+    var grade: String?          // 10, 9.5
+    var certNumber: String?     // 123456
+    var isCustomValuation: Bool = false
+    var isSerialized: Bool? = false
+    var currencyCode: String?
+
+    init(from scan: CardMetadata, imageName: String, collection: String, location: String) {
+        self.id = UUID()
+        self.scryfallID = "\(scan.setCode)-\(scan.collectorNumber)"
+        self.name = scan.name
+        self.setCode = scan.setCode
+        self.collectorNumber = scan.collectorNumber
+        self.imageFileName = imageName
+        self.condition = AppConfig.Defaults.defaultCondition
+        self.foilType = AppConfig.Defaults.defaultFoil
+        self.currentValuation = scan.priceScanned
+        self.previousValuation = scan.priceScanned
+        self.dateAdded = Date()
+        self.classification = "Unknown"
+        self.collectionName = collection
+        self.storageLocation = location
+        self.rarity = scan.rarity
+        self.colorIdentity = scan.colorIdentity
+        self.isSerialized = scan.isSerialized
+    }
+
+    /// Full memberwise init used by SavedCardModel (SwiftData) ↔ SavedCard conversion.
+    init(id: UUID, scryfallID: String, name: String, setCode: String, collectorNumber: String,
+         imageFileName: String, condition: String, foilType: String, currentValuation: Double?,
+         previousValuation: Double?, dateAdded: Date, classification: String, collectionName: String,
+         storageLocation: String, rarity: String?, colorIdentity: [String]?,
+         gradingService: String?, grade: String?, certNumber: String?,
+         isCustomValuation: Bool, isSerialized: Bool?, currencyCode: String?) {
+        self.id = id
+        self.scryfallID = scryfallID
+        self.name = name
+        self.setCode = setCode
+        self.collectorNumber = collectorNumber
+        self.imageFileName = imageFileName
+        self.condition = condition
+        self.foilType = foilType
+        self.currentValuation = currentValuation
+        self.previousValuation = previousValuation
+        self.dateAdded = dateAdded
+        self.classification = classification
+        self.collectionName = collectionName
+        self.storageLocation = storageLocation
+        self.rarity = rarity
+        self.colorIdentity = colorIdentity
+        self.gradingService = gradingService
+        self.grade = grade
+        self.certNumber = certNumber
+        self.isCustomValuation = isCustomValuation
+        self.isSerialized = isSerialized
+        self.currencyCode = currencyCode
+    }
+}
+
+enum MatchResult {
+    case exact(CardMetadata)
+    case ambiguous(name: String, candidates: [CardMetadata])
+    case unknown
+}