add security py

backend/settings.py

@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 import os
 from pathlib import Path
 from typing import Any
@@ -13,6 +15,7 @@ class Settings(BaseSettings):
     workers: int = 1
     log_level: str = "info"
     database_url: str = "sqlite:///:memory:"
+    hmac_key: str | None = None
 
     model_config = ConfigDict(env_file=".env", env_file_encoding="utf-8")