update auth.py

backend/auth.py

@@ -3,8 +3,12 @@ import bcrypt
 from jose import jwt, JWTError
 from datetime import datetime, timedelta
 from fastapi import Header, HTTPException
+from dotenv import load_dotenv
+import os   
 
-SECRET_KEY = ""
+load_dotenv()
+
+SECRET_KEY = os.getenv("SECRET_KEY")
 ALGORITHM = "HS256"