Add version badge to sidebar footer showing installed vs latest version,
fetched from /api/nixserver/system/version. Badge shows green when up to
date or amber with target version when an update is available.
Upgrade button triggers POST /api/nixserver/system/upgrade which spawns
scripts/update.sh detached (git pull + npm install + prisma migrate +
build + restart). Response is returned before the service restarts so
the client receives confirmation. Panel comes back online in ~60 s.
NixReaper
a0e3fc7b1e