basement: add data dir bind mount (/var/lib/basement-ui)

Last config blocker — basement-ui's store.Open() calls MkdirAll on
BASEMENT_DATA_DIR (default /var/lib/basement-ui), which fails inside
the container because / is read-only-ish for the unprivileged user.

Mount /mnt/user/appdata/basement to /var/lib/basement-ui via a Path
Config; install.sh pre-creates the directory (and host-agent's
appdata while we're at it, since we never explicitly created that
either — it had been working by luck).

Source-checked the basement-ui repo for any other "is required" env
vars; ADMIN_USER / ADMIN_PASSWORD_HASH / JWT_SECRET / DRIVER (+ the
two DRIVER_GARAGE_* when DRIVER=garage) are the complete set. After
this, container should reach Up.

unraid-1/install.sh

@@ -38,7 +38,7 @@ die() { printf "install.sh: %s\n" "$*" >&2; exit 1; }
 [ -d /mnt/user ]                       || die "/mnt/user missing — is the array started?"
 [ -d /mnt/user/s3 ]                    || die "share /mnt/user/s3 missing. Create it in unraid UI first (Shares → Add Share → 's3', cache:yes recommended), then re-run."
 
-mkdir -p "$APPDATA/meta" "$DATADIR" "$TEMPLATE_DIR"
+mkdir -p "$APPDATA/meta" "$DATADIR" "$TEMPLATE_DIR" /mnt/user/appdata/basement /mnt/user/appdata/host-agent
 
 # ── garage.toml ──
 if [ -f "$TOML_DEST" ] && [ "${FORCE:-}" != "1" ]; then