fix prod backend url

Author: AnthonyGress

frontend/src/constants/constants.ts

@@ -12,7 +12,7 @@ export const initialItems = [
 ];
 
 export const BACKEND_URL = import.meta.env.VITE_BACKEND_URL || (
-    import.meta.env.MODE === 'production' ? '' : 'http://localhost:5000'
+    import.meta.env.PROD ? '' : 'http://localhost:5000'
 );
 
 export const FIFTEEN_MIN_IN_MS = 900000;