--surface-hover and --sidebar-border weren't defined in the site's :root (and
--sidebar-bg had a made-up value), so the category hover/active background and
the row separators resolved to nothing — the sidebar looked flat vs the App
Center. Set them to the exact nebula values.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Signed-off-by: librelad <librelad@digitalangels.vip>