fix bug userid

NLP_model/chatbot.py

@@ -198,7 +198,7 @@ def generate_cache_key(request, user_id):
     # Tạo MD5 hash
     return hashlib.md5(combined.encode()).hexdigest()
 
-def chat(request, user_id="default_user"):
+def chat(request, user_id=0):
     """Process a chat request from a specific user"""
     start_time = time.time()