At startup the app runs `cv4pve-cli --version`. If it differs from cli.TESTED_VERSION (2.4.0), a warning says which version was found and which one was tested. The app parses output formats that are not a stable API: the config list text, prune-backups as a JSON string, the CT ip-addresses JSON string and the exit codes with --wait. A newer cv4pve-cli could break them in confusing ways. If cv4pve-cli cannot be run at all, an error says so once, instead of every later call failing without explanation. The README notes the tested version. Closes #14 Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>