added TYPE_CHECKING to heater main.py

python/heater/main.py

@@ -1,9 +1,9 @@
 """FastAPI heater control service."""
+from __future__ import annotations
 
 import logging
-from collections.abc import AsyncIterator
 from contextlib import asynccontextmanager
-from typing import Annotated
+from typing import TYPE_CHECKING, Annotated
 
 import typer
 import uvicorn
@@ -13,6 +13,9 @@ from python.common import configure_logger
 from python.heater.controller import HeaterController
 from python.heater.models import ActionResult, DeviceConfig, HeaterStatus
 
+if TYPE_CHECKING:
+    from collections.abc import AsyncIterator
+
 logger = logging.getLogger(__name__)