Replace spoofable Host/Origin WebSocket auth with short-lived bootstrap
tokens minted over the existing local-operator HTTP path. Docker/browser
shell sessions prefetch a token before connecting; loopback peers remain
unchanged.
Also bump backend ws to 8.21.0 and refresh frontend lockfile to clear
npm audit findings (dev toolchain only for frontend).
Fixes#405, #406, #407
Co-authored-by: Cursor <cursoragent@cursor.com>