v2.6.6

Fixed

• Startup version check update path installed the wrong version. _startup_version_check discovered the target version via the GitHub releases API, but then delegated to cmd_update which always downloaded from the main branch raw URL. GitHub's CDN can serve a stale version of the main branch for a short time after a push, causing the installed script to report the previous version number. _startup_version_check now passes the target version to cmd_update, which downloads from the immutable tag ref (/v{version}/proxmox-lab.sh) instead of /main/. The interactive update path (menu option 10) is unchanged and continues to download from main.