fix: close deployment decoupling review

deploy/compose.session-server.yaml.example

@@ -20,7 +20,7 @@ services:
       - source: session_ca
         target: session_ca.pem
     volumes:
-      - ./deploy/workspaces:/app/harness/workspaces:ro
+      - ${THT_SERVER_WORKSPACE_CONFIG:?set THT_SERVER_WORKSPACE_CONFIG}:/app/harness/workspaces/server-sessions.yaml:ro
 
   # Run manually during the maintenance window. It is not a dependency of core,
   # so the application never gains the schema-changing migrator credential.