Make fido2 property a lazy var

- This object was being kept around after being created and as we need it in some other functions it made sense to make it lazy and keep it around that way.
- Arguably the FIDO2 instance could be removed after each time it’s been used, but as the FIDO2 class doesn’t have any state stored in it, it seems benign keeping it about for now.

Xcodes/Backend/AppState.swift

@@ -355,8 +355,8 @@ class AppState: ObservableObject {
             .store(in: &cancellables)
     }
     
-    var fido2: FIDO2?
-    
+    private lazy var fido2 = FIDO2()
+
     func createAndSubmitSecurityKeyAssertationWithPinCode(_ pinCode: String?, sessionData: AppleSessionData, authOptions: AuthOptionsResponse) {
         self.presentedSheet = .securityKeyTouchToConfirm
         
@@ -379,8 +379,6 @@ class AppState: ObservableObject {
 
         Task {
             do {
-                let fido2 = FIDO2()
-                self.fido2 = fido2
                 let response = try fido2.respondToChallenge(args: ChallengeArgs(rpId: rpId, validCredentials: validCreds, devPin: pinCode, challenge: challenge, origin: origin))
             
                 Task { @MainActor in
@@ -413,7 +411,7 @@ class AppState: ObservableObject {
     }
     
     func cancelSecurityKeyAssertationRequest() {
-        self.fido2?.cancel()
+        self.fido2.cancel()
     }
     
     private func handleAuthenticationFlowCompletion(_ completion: Subscribers.Completion<Error>) {