CVE-2026-45626: Arcane Backend: OS Command Injection in Volume Browser ListDirectory via path query parameter

GET /environments/{id}/volumes/{volumeName}/browse accepts a path query parameter that is passed to a shell command (sh -c "find … | while …") inside an Arcane helper container. The path sanitiser blocks ../ traversal but does not strip Bourne-shell metacharacters such as $() or backticks, and strconv.Quote only escapes Go string metacharacters, not shell substitution sequences. Any authenticated user with access to a browseable volume can execute arbitrary commands inside the helper container; command output is reflected back in the 500 error body.