Update error message to mention HF Spaces secrets

backend/llm.py

@@ -15,7 +15,8 @@ _GROQ_API_KEY = os.getenv("GROQ_API_KEY", "")
 if not _GROQ_API_KEY or _GROQ_API_KEY == "your_groq_api_key_here":
     raise RuntimeError(
         "GROQ_API_KEY is not set. "
-        "Please add your key to the .env file in the project root."
+        "Please add your key to the .env file in the project root, "
+        "or set it as a Secret in your Hugging Face Space settings."
     )
 
 # Shared LLM instance – llama-3.3-70b-versatile on Groq for speed + quality