docs: add hf_oauth + apache-2.0 license to README front-matter

hf_oauth: true is what wires the LoginButton + OAuth callback the
Submit tab relies on; without it the auth-required submit flow is
silently broken (login click no-ops, no token reaches the handler).

license: apache-2.0 matches the HF Leaderboards template
(gradio-templates/leaderboard) and the rest of the cadgenbench code
surface, and renders a license badge on the Space page.

README.md

@@ -6,6 +6,8 @@ colorTo: pink
 sdk: docker
 app_port: 7860
 pinned: true
+license: apache-2.0
+hf_oauth: true
 short_description: Leaderboard for AI-driven CAD generation
 ---