basement: rename image basement-ui -> basement; chown appdata for distroless

- template Repository now ghcr.io/mattjackson/basement:latest
- Registry URL and all "basement-ui" descriptive text updated
- install.sh chowns /mnt/user/appdata/basement to 65532:65532 so the
  nonroot distroless image can create its data subpaths

unraid-1/install.sh

@@ -39,6 +39,10 @@ die() { printf "install.sh: %s\n" "$*" >&2; exit 1; }
 [ -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" /mnt/user/appdata/basement /mnt/user/appdata/host-agent
+# basement image is distroless and runs as nonroot UID 65532 — it can't mkdir
+# subpaths under a root-owned bind mount target. host-agent runs as root, so
+# only the basement dir needs this.
+chown 65532:65532 /mnt/user/appdata/basement
 
 # ── garage.toml ──
 if [ -f "$TOML_DEST" ] && [ "${FORCE:-}" != "1" ]; then