Turn NeoChatConnection::isVerifiedSession into a notifiable property

This should allow the devices page to hide the "Verify this Device"
warning, once you actually complete verification. I also made sure to
update the other consumer - the menu item under the user menu.

Additionally, I also fixed the password field not being automatically
focused when trying to remove a device.

src/app/qml/KeyVerificationDialog.qml

@@ -4,6 +4,7 @@
 import QtQuick
 import QtQuick.Controls as QQC2
 import QtQuick.Layouts
+import QtQuick.Window
 import QtQml
 
 import org.kde.kirigami as Kirigami
@@ -170,6 +171,7 @@ Kirigami.Page {
                     return "";
                 }
             }
+            onDone: root.QQC2.Window.window.close()
         }
     }