copr/anubis: fix configuration on frontend to protect only /coprs (same for distgit)

Anubis was accidentally enabled for all traffic (/) instead of just
the /coprs/ web UI. This caused unnecessary bot challenges for API
clients, dnf/yum, and other automated tools.

Use Anubis BASE_PREFIX to cleanly protect only specific endpoints:
- Frontend: /coprs/ (web UI)
- Dist-git: /{{ cgit_uri }}/ (package browser)

https://anubis.techaro.lol/docs/admin/installation#using-base-prefix

roles/copr/frontend/templates/httpd/coprs.conf

@@ -85,8 +85,13 @@ WSGIApplicationGroup %{GLOBAL}
     ProxyRequests Off
     ProxyVia Off
 
-    ProxyPass / http://127.0.0.1:8987/
-    ProxyPassReverse / http://127.0.0.1:8987/
+    # /coprs/ goes through Anubis (configured with BASE_PREFIX=/coprs)
+    ProxyPass /coprs/ http://127.0.0.1:8987/coprs/
+    ProxyPassReverse /coprs/ http://127.0.0.1:8987/coprs/
+
+    # Everything else goes directly to backend
+    ProxyPass / http://127.0.0.1:8345/
+    ProxyPassReverse / http://127.0.0.1:8345/
 </VirtualHost>