- SshSession::resetConnection(): force-disconnect before each new top-level

backup operation so ssh_scp_new() doesn't fail on a reused stale session
  (reproduces as 'Failed to open channel for scp' right after restore)
- Call resetConnection() at entry of createBackup() and uploadBackup()
- Replace recursive findStackView() in PageSetupWizardEasy with upward
  parent traversal (depth+push check) to avoid JS stack overflow on iOS
  when component tree is large (71 VPN managers in test)

client/ui/controllers/serversBackupController.cpp

@@ -62,6 +62,8 @@ void ServersBackupController::createBackup(const ServerCredentials &credentials)
         return;
     }
 
+    m_sshSession.resetConnection();
+
     setStatus(InProgress);
     setProgress(0, tr("Starting backup creation..."));
 
@@ -482,6 +484,8 @@ void ServersBackupController::uploadBackup(const ServerCredentials &credentials,
         return;
     }
 
+    m_sshSession.resetConnection();
+
     // Save restore mode for later use
     m_restoreReplaceMode = replaceMode;