Update GPT model to 'gpt-4o-mini' for chat functionality in app.py

website/app.py

@@ -981,7 +981,7 @@ def chat_with_assistant():
     
     try:
         response = client.chat.completions.create(
-            model="gpt-3.5-turbo-16k",
+            model="gpt-4o-mini",
             messages=api_messages,
             max_tokens=300,
             temperature=0.7