🩹(backend) update HasPrivilegesOnRoom permission error message

Generalize error message in HasPrivilegesOnRoom permission class to reflect
its broader usage beyond just recording contexts. Improves clarity when
this permission check fails in various application scenarios.

src/backend/core/api/permissions.py

@@ -94,7 +94,7 @@ class HasAbilityPermission(IsAuthenticated):
 class HasPrivilegesOnRoom(IsAuthenticated):
     """Check if user has privileges on a given room."""
 
-    message = "You must have privileges to start a recording."
+    message = "You must have privileges on room to perform this action."
 
     def has_object_permission(self, request, view, obj):
         """Determine if user has privileges on room."""