Isolate observation collector from web API

web/observation_collector_worker.py

@@ -0,0 +1,47 @@
+"""Standalone observation collector process.
+
+The FastAPI web worker must stay responsive for health checks and user-facing
+API routes. High-frequency source polling runs here instead of inside the web
+request process.
+"""
+
+from __future__ import annotations
+
+import signal
+import threading
+from types import FrameType
+from typing import Optional
+
+from loguru import logger
+
+from web.core import _weather
+from web.observation_collector_service import start_observation_collector_loop
+from web.services.city_runtime import _refresh_city_panel_cache
+
+_STOP_EVENT = threading.Event()
+
+
+def _handle_stop_signal(signum: int, _frame: Optional[FrameType]) -> None:
+    logger.info("observation collector worker stopping signal={}", signum)
+    _STOP_EVENT.set()
+
+
+def main() -> None:
+    signal.signal(signal.SIGINT, _handle_stop_signal)
+    signal.signal(signal.SIGTERM, _handle_stop_signal)
+
+    thread = start_observation_collector_loop(
+        weather=_weather,
+        cache_refresher=lambda city: _refresh_city_panel_cache(city, force_refresh=False),
+    )
+    if thread is None:
+        logger.warning("observation collector worker started with collector disabled")
+    else:
+        logger.info("observation collector worker started thread={}", thread.name)
+
+    while not _STOP_EVENT.wait(3600):
+        pass
+
+
+if __name__ == "__main__":
+    main()