Add QR scanner support for macOS with camera selection

- Refactor QR scanner into separate Scanner module for iOS and macOS
- Add camera selection menu for devices with multiple cameras
- Use Vision framework for QR detection on macOS
- Remove tvOS QR scanner support (continuity camera)
- Add camera entitlement and usage description for macOS
- Fix minor issues in Intents and ExtensionProvider

ApplicationLibrary/Views/Scanner/QRScanner.swift

@@ -0,0 +1,32 @@
+import AVFoundation
+import SwiftUI
+
+public enum QRScanError: Error, LocalizedError {
+    case cameraUnavailable
+    case permissionDenied
+    case scanFailed(Error)
+    case invalidCode
+
+    public var errorDescription: String? {
+        switch self {
+        case .cameraUnavailable:
+            return String(localized: "Camera is not available")
+        case .permissionDenied:
+            return String(localized: "Camera access denied")
+        case let .scanFailed(error):
+            return error.localizedDescription
+        case .invalidCode:
+            return String(localized: "Invalid QR code")
+        }
+    }
+}
+
+public struct QRScanResult: Sendable {
+    public let string: String
+    public let type: AVMetadataObject.ObjectType
+
+    public init(string: String, type: AVMetadataObject.ObjectType) {
+        self.string = string
+        self.type = type
+    }
+}