basement-ui's config loader namespaces driver-specific settings under
BASEMENT_DRIVER_<DRIVER>_*. With DRIVER=garage, it looks for:
BASEMENT_DRIVER_GARAGE_ADMIN_URL
BASEMENT_DRIVER_GARAGE_ADMIN_TOKEN
not the bare GARAGE_ADMIN_URL / GARAGE_ADMIN_TOKEN we had.
Value still the same (same admin URL, same admin token from secrets.env);
just the Target env var name changes. install.sh's sed substitution of
__GARAGE_ADMIN_TOKEN__ still applies — it's a value placeholder, not the
env var name.