docs: document full and embedded rendering with server authentication

docs/installazione-docker-4-contesti.md

@@ -1,5 +1,13 @@
 # Docker installation in the current operating contexts
 
+Rendering and authentication are independent of these Docker contexts. Explicitly
+select full/en for the Mac, full/OIDC for an autonomous server, or
+embedded/upstream for Omics. The same frontend image supports both renderings;
+generated `config.js` and the host page decide the container, while the backend
+and trusted proxy decide identity. See [shell configuration and deploy](operations/shell-and-localization.md)
+and [server portal authentication](install/authentication-upstream.md). Do not
+apply the standalone server authentication projection to the Omics upstream path.
+
 ThothII uses one Compose topology:
 
 - `frontend`