ingest: graceful shutdown on SIGTERM

Handle SIGTERM (and SIGINT) to stop the HTTP server cleanly instead of being
killed after Docker's grace period, so `docker compose down` returns in ~1s and
the queue, HTTP clients and database are closed properly. shutdown() runs on a
helper thread since it must not run on the serving thread.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

ingest/radieo/__main__.py

@@ -1,6 +1,8 @@
 """Entry point: wire providers/fetchers into the queue and serve GET /next."""
 
 import logging
+import signal
+import threading
 
 from . import config
 from .api import IngestServer
@@ -159,6 +161,17 @@ def main() -> None:
         config.CACHE_DIR,
         config.STATE_DB,
     )
+
+    # Shut down cleanly on `docker compose down` (SIGTERM) instead of being
+    # killed after the grace period. shutdown() must run off the serving
+    # thread, so hand it to a helper thread.
+    def _handle_signal(signum, _frame):
+        log.info("received signal %d, shutting down", signum)
+        threading.Thread(target=server.shutdown, daemon=True).start()
+
+    signal.signal(signal.SIGTERM, _handle_signal)
+    signal.signal(signal.SIGINT, _handle_signal)
+
     try:
         server.serve_forever()
     except KeyboardInterrupt: