Refactor model scene definitions

web/public/locales/en/config/validation.json

@@ -33,6 +33,7 @@
     "dimensionMustBeEven": "Must be an even number."
   },
   "models": {
-    "defaultRequired": "One model must use a scene of 'All cameras'. Without it, any camera that does not choose a scene has no model to fall back to."
+    "defaultRequired": "One model must use the default scene. Without it, any camera that does not choose a scene has no model to fall back to.",
+    "sceneDuplicate": "Each model must use a different scene."
   }
 }