Fix: pop-to-root during Sign Out to work around warning

- Warning encountered on iOS 18 when signing out:
> The `navigationDestination` modifier only works inside a `NavigationStack` or `NavigationSplitView`. Theres

BikeIndex/View/Settings/SettingsPage.swift

@@ -50,7 +50,7 @@ struct SettingsPage: View {
                         Label("Registration Organization", systemImage: "person.badge.shield.checkmark")
                     }
 
-                    Button(action: client.destroySession) {
+                    Button(action: logout) {
                         Label("Sign out", systemImage: "figure.walk.departure")
                             .tint(Color.highlightPrimary)
                             .foregroundStyle(Color.highlightPrimary)
@@ -171,6 +171,11 @@ struct SettingsPage: View {
         }
     }
 
+    func logout() {
+        path = NavigationPath()
+        client.destroySession()
+    }
+
     /// Excluding signOut and contactUs which don't navigate internally
     enum SettingsSelection: Hashable, Identifiable {
         var id: Self { self }