Enable automatic refetching for event theme queries

Added `refetchOnWindowFocus` and `refetchIntervalInBackground` options to the event theme query. This ensures data stays updated when switching tabs or in the background.

frontend/src/context/event-theme-context.tsx

@@ -97,6 +97,8 @@ export const EventThemesProvider: React.FC<EventThemesProviderProps> = ({
     error,
   } = useQuery({
     ...listEventThemesOptions(),
+    refetchOnWindowFocus: "always",
+    refetchIntervalInBackground: true,
   });
 
   // Fetch specific theme