Separate og:site_name from App Name

The OpenGraph og:site_name property is currently tied directly to App Name. This creates a forced trade-off — if you want a clean brand name in social previews (e.g. "Rollabooth"), you can't also use App Name flexibly elsewhere in the platform.

Please expose og:site_name as a separate, customer-configurable field in the SEO panel so we can keep social previews clean regardless of how App Name is used.