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/Persistence/ImageManager.swift

@@ -0,0 +1,137 @@
+import UIKit
+import Foundation
+
+// MARK: - IMAGE MANAGER
+// All card images and user content are stored in a dedicated UserContent/ subfolder
+// inside either iCloud Drive/Documents/ or the local Documents directory.
+// This keeps binary files separate from the SwiftData store and aligns with the
+// blueprint's requirement for a named UserContent container in iCloud Drive.
+
+class ImageManager {
+
+    // MARK: - Directory Helpers
+
+    /// Active working directory: iCloud Documents/UserContent/ or local Documents/UserContent/.
+    static var dir: URL {
+        let base: URL
+        if FileManager.default.ubiquityIdentityToken != nil,
+           let cloud = FileManager.default.url(forUbiquityContainerIdentifier: nil) {
+            base = cloud.appendingPathComponent("Documents")
+        } else {
+            base = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask)[0]
+        }
+        let userContent = base.appendingPathComponent("UserContent")
+        if !FileManager.default.fileExists(atPath: userContent.path) {
+            try? FileManager.default.createDirectory(at: userContent, withIntermediateDirectories: true)
+        }
+        return userContent
+    }
+
+    /// The pre-UserContent base directory. Used only for one-time migration; not for new I/O.
+    private static var legacyDir: URL {
+        if FileManager.default.ubiquityIdentityToken != nil,
+           let cloud = FileManager.default.url(forUbiquityContainerIdentifier: nil) {
+            return cloud.appendingPathComponent("Documents")
+        }
+        return FileManager.default.urls(for: .documentDirectory, in: .userDomainMask)[0]
+    }
+
+    // MARK: - Save / Load / Delete
+
+    static func save(_ img: UIImage, name: String) throws {
+        let url = dir.appendingPathComponent(name)
+
+        let maxSize: CGFloat = 1024
+        var actualImg = img
+        if img.size.width > maxSize || img.size.height > maxSize {
+            let scale = maxSize / max(img.size.width, img.size.height)
+            let newSize = CGSize(width: img.size.width * scale, height: img.size.height * scale)
+            let format = UIGraphicsImageRendererFormat()
+            format.scale = 1
+            let renderer = UIGraphicsImageRenderer(size: newSize, format: format)
+            actualImg = renderer.image { _ in img.draw(in: CGRect(origin: .zero, size: newSize)) }
+        }
+
+        guard let data = actualImg.jpegData(compressionQuality: 0.7) else { return }
+        try data.write(to: url, options: .atomic)
+    }
+
+    static func load(name: String) -> UIImage? {
+        let p = dir.appendingPathComponent(name)
+        if FileManager.default.fileExists(atPath: p.path) { return UIImage(contentsOfFile: p.path) }
+        try? FileManager.default.startDownloadingUbiquitousItem(at: p)
+        return UIImage(contentsOfFile: p.path)
+    }
+
+    static func delete(name: String) async {
+        let url = dir.appendingPathComponent(name)
+        try? FileManager.default.removeItem(at: url)
+    }
+
+    // MARK: - Migration
+
+    /// Moves JPG images from the legacy flat directory into the UserContent/ subfolder.
+    /// Called once during the SwiftData migration in BackgroundPersistenceActor.
+    static func migrateImagesToUserContent() {
+        let oldDir = legacyDir
+        let newDir = dir
+
+        guard let files = try? FileManager.default.contentsOfDirectory(
+            at: oldDir, includingPropertiesForKeys: nil
+        ) else { return }
+
+        var moved = 0
+        for file in files where file.pathExtension == "jpg" {
+            let dest = newDir.appendingPathComponent(file.lastPathComponent)
+            if !FileManager.default.fileExists(atPath: dest.path) {
+                try? FileManager.default.moveItem(at: file, to: dest)
+                moved += 1
+            }
+        }
+        if moved > 0 { print("MIGRATION: Moved \(moved) images → UserContent/") }
+    }
+
+    /// Legacy: moves images from local Documents to iCloud Documents/UserContent/.
+    /// Retained for compatibility but superseded by migrateImagesToUserContent().
+    static func migrateToCloud() {
+        guard let cloudBase = FileManager.default.url(forUbiquityContainerIdentifier: nil)?
+            .appendingPathComponent("Documents") else { return }
+        let cloudURL = cloudBase.appendingPathComponent("UserContent")
+        let localURL = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask)[0]
+
+        if !FileManager.default.fileExists(atPath: cloudURL.path) {
+            try? FileManager.default.createDirectory(at: cloudURL, withIntermediateDirectories: true)
+        }
+
+        guard let files = try? FileManager.default.contentsOfDirectory(
+            at: localURL, includingPropertiesForKeys: nil
+        ) else { return }
+        for file in files where file.pathExtension == "jpg" {
+            let dest = cloudURL.appendingPathComponent(file.lastPathComponent)
+            if !FileManager.default.fileExists(atPath: dest.path) {
+                try? FileManager.default.moveItem(at: file, to: dest)
+            }
+        }
+    }
+
+    // MARK: - Cleanup
+
+    static func cleanupOrphans(activeImages: Set<String>) {
+        Task.detached {
+            guard !activeImages.isEmpty else { return }
+            let fileManager = FileManager.default
+            guard let files = try? fileManager.contentsOfDirectory(
+                at: dir, includingPropertiesForKeys: [.contentModificationDateKey]
+            ) else { return }
+
+            for fileURL in files where fileURL.pathExtension == "jpg" {
+                if !activeImages.contains(fileURL.lastPathComponent),
+                   let attrs = try? fileManager.attributesOfItem(atPath: fileURL.path),
+                   let date = attrs[.modificationDate] as? Date,
+                   Date().timeIntervalSince(date) > 3600 {
+                    try? fileManager.removeItem(at: fileURL)
+                }
+            }
+        }
+    }
+}