Simplify key backup unlocking

Replaces the separate text fields for security keys and backup passphrases with a single on; internally, both methods are then tried.

src/libneochat/neochatconnection.h

@@ -222,6 +222,8 @@ public:
      */
     bool isVerifiedSession() const;
 
+    Q_INVOKABLE void unlockSSSS(const QString &secret);
+
 Q_SIGNALS:
     void globalUrlPreviewEnabledChanged();
     void labelChanged();
@@ -259,6 +261,9 @@ Q_SIGNALS:
      */
     void ownSessionVerified();
 
+    void keyBackupUnlocked();
+    void keyBackupError();
+
 private:
     static bool m_globalUrlPreviewDefault;
     static PushRuleAction::Action m_defaultAction;