PCM dev 9a321a2 - fix(gtk3): fix critici e alti su connessioni remote

fix(gtk3): fix critici e alti su connessioni remote

• log_viewer: command injection fix (shlex.quote su extra field)
• cron_widget: race condition fix (threading.Lock + _write_pending)
• winscp_widget: leak SSH/SFTP transfer connection in chiudi_processo
• winscp_widget: idle_add throttling ogni 100ms (non piu' per-chunk)
• winscp_widget: BUG CRITICO upload/download invertito nel ramo upload
• sftp_editor: temp file cleanup su destroy handler
• keepassxc_manager: subprocess leak fix con try/finally
• rdp_widget: zombie processes (Popen->subprocess.run), resize throttling
• tunnel_manager: override_color deprecato -> CSS provider
• vnc_widget: dead code rimosso (if False), 'tigervnc' -> 'tigervncviewer'