chore: import upstream snapshot with attribution

ios/Sources/JCodeMobile/QRScannerView.swift

@@ -0,0 +1,103 @@
+import AVFoundation
+import SwiftUI
+
+/// Camera-based QR scanner for pairing codes.
+struct QRScannerView: UIViewControllerRepresentable {
+    let onScan: (String) -> Void
+
+    func makeUIViewController(context: Context) -> ScannerViewController {
+        let controller = ScannerViewController()
+        controller.onScan = onScan
+        return controller
+    }
+
+    func updateUIViewController(_ controller: ScannerViewController, context: Context) {}
+}
+
+final class ScannerViewController: UIViewController, @preconcurrency AVCaptureMetadataOutputObjectsDelegate {
+    var onScan: ((String) -> Void)?
+
+    private let session = AVCaptureSession()
+    private var previewLayer: AVCaptureVideoPreviewLayer?
+    private var didScan = false
+
+    override func viewDidLoad() {
+        super.viewDidLoad()
+        view.backgroundColor = .black
+
+        guard let device = AVCaptureDevice.default(for: .video),
+            let input = try? AVCaptureDeviceInput(device: device),
+            session.canAddInput(input)
+        else {
+            showUnavailableLabel()
+            return
+        }
+        session.addInput(input)
+
+        let output = AVCaptureMetadataOutput()
+        guard session.canAddOutput(output) else {
+            showUnavailableLabel()
+            return
+        }
+        session.addOutput(output)
+        output.setMetadataObjectsDelegate(self, queue: .main)
+        output.metadataObjectTypes = [.qr]
+
+        let preview = AVCaptureVideoPreviewLayer(session: session)
+        preview.videoGravity = .resizeAspectFill
+        preview.frame = view.bounds
+        view.layer.addSublayer(preview)
+        previewLayer = preview
+    }
+
+    override func viewDidLayoutSubviews() {
+        super.viewDidLayoutSubviews()
+        previewLayer?.frame = view.bounds
+    }
+
+    override func viewWillAppear(_ animated: Bool) {
+        super.viewWillAppear(animated)
+        didScan = false
+        let session = session
+        DispatchQueue.global(qos: .userInitiated).async {
+            if !session.isRunning {
+                session.startRunning()
+            }
+        }
+    }
+
+    override func viewWillDisappear(_ animated: Bool) {
+        super.viewWillDisappear(animated)
+        let session = session
+        DispatchQueue.global(qos: .userInitiated).async {
+            if session.isRunning {
+                session.stopRunning()
+            }
+        }
+    }
+
+    func metadataOutput(
+        _ output: AVCaptureMetadataOutput,
+        didOutput metadataObjects: [AVMetadataObject],
+        from connection: AVCaptureConnection
+    ) {
+        guard !didScan,
+            let object = metadataObjects.first as? AVMetadataMachineReadableCodeObject,
+            object.type == .qr,
+            let value = object.stringValue
+        else { return }
+        didScan = true
+        UINotificationFeedbackGenerator().notificationOccurred(.success)
+        onScan?(value)
+    }
+
+    private func showUnavailableLabel() {
+        let label = UILabel()
+        label.text = "Camera unavailable"
+        label.textColor = .white
+        label.textAlignment = .center
+        label.frame = view.bounds
+        label.autoresizingMask = [.flexibleWidth, .flexibleHeight]
+        view.addSubview(label)
+    }
+}