allow for empty hf token

app.py

@@ -88,6 +88,9 @@ def route_and_plot(model_choice: str, hf_token: str, user_prompt: str, assistant
     - Call backend (real or mock)
     - Return a table + bar plot + status message
     """
+    if hf_token.strip() == "":
+        hf_token = None  # allow empty token
+
     model_id = model_choice.strip()
     if not model_id:
         raise gr.Error("Please select a model or enter a custom model id.")