Add plogical/cyberpanel_python.py with resolve_cyberpanel_python() and
ensure_cyberpanel_bin_python_shim() (symlink to system Python when venv
binary is absent). Call shim before writing root crontab on install/upgrade,
and from IncBackups/IncScheduler.py so existing jobs self-heal. IncBackups
views use resolved interpreter for backupUtilities. Upgrade._python_for_manage
delegates to resolve_cyberpanel_python().
