v1.2.13 - Auth add-on 1.8.0 (pre-release) - Fix noVNC "Connecting…" hang (#136)

⚠️ Pre-release, needs field testing.
This rewrites the auth container's display backend to fix #136 (noVNC stuck on "Connecting…").
The change was validated in logic, but not on a machine that reproduces the original crash.
Please test before relying on it; feedback welcome on #136.

Fixed

• noVNC no longer hangs on "Connecting…" forever (#136). The display stack
  (Xvfb + fluxbox + x11vnc + websockify) used to fail completely silently: the container
  reported healthy while VNC was dead.
  • Display processes now log to files / journald and are liveness-checked, so failures
    surface in docker logs instead of vanishing.
  • Stale /tmp/.X11-unix/X99 state is cleaned on start, fixing VNC dying silently after
    a docker restart.
  • The VNC password is truncated to the 8 characters DES actually uses, and the
    auto-connect URL now matches.

Changed

• TigerVNC (Xvnc) is now the default display backend, replacing x11vnc, whose 2019
  build crashed on client connect against bookworm's libraries. Xvnc serves VNC natively:
  no Xvfb, no screen scraper.
  • The legacy Xvfb + x11vnc stack remains as an automatic fallback.
  • Force a backend with FAMILYLINK_VNC_BACKEND=tigervnc|x11vnc.

Thanks

Huge thanks to @wookash for the strace-level diagnosis that pinpointed the crash and the two
silent-failure traps around it.