Try to build the frontend and the backend and see if its update

backend/main.py

@@ -24,7 +24,7 @@ DATA_FILE = "diagram.json"
 
 @app.get("/")
 def root():
-    return {"message": "Check if the API is running"}
+    return {"message": "Check if the server is running"}
 
 @app.get("/diagram/fetch")
 def fetch_diagram():

frontend/src/App.jsx

@@ -4,4 +4,4 @@ function App() {
   return <Diagram />;
 }
 
-export default App;
+export default App;