Editing blocked on frozen sites during migration (v4.99.3)

Save, publish, branch creation, and review requests are now refused server-side when a site is frozen for migration, preventing content loss during the cutover window.

Broken sandbox images now load correctly (v4.99.3)

Asset images that failed in every browser due to a TLS certificate mismatch on the legacy host are now served from the correct CDN and display as expected.