Update to upstream Spaces 0.3.0 and refresh bundled images (subs v0.1.2c,
certrelay v0.2.8, nacho v1.0.0b). Add Create/Show Registry API Keys for
registry-server, remove Configure Subspaces and SUBS_PUBLISH_REQUIRE_FINALIZED,
and align README/instructions with the new tags.
Co-authored-by: Cursor <cursoragent@cursor.com>
