update to use HF secret

app.py

@@ -44,8 +44,7 @@ h1 {
 def generate_prompt():
     try:
         # Read the system prompt from file
-        with open("system_prompt.md", "r") as f:
-            system_prompt = f.read()
+        system_prompt = os.environ.get("SYSTEM_PROMPT")
 
         # Initialize OpenAI client
         client = OpenAI(api_key=os.environ.get("OPENAI_API_KEY"))