Add recording cleanup container to remove noise files

Alpine-based sdr-cleanup container runs a find loop every 5 minutes,
deleting MP3 files under 3 KB (configurable via SIZE_THRESHOLD env var)
to keep the web browser and Samba share free of false-positive recordings.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

docker-compose.yml

@@ -18,3 +18,15 @@ services:
     volumes:
       - ./nginx.conf:/etc/nginx/conf.d/default.conf:ro
       - /home/m/recordings:/recordings:ro
+
+  cleanup:
+    image: alpine:latest
+    container_name: sdr-cleanup
+    restart: unless-stopped
+    environment:
+      - SIZE_THRESHOLD=3k
+      - INTERVAL=300
+    volumes:
+      - ./cleanup-recordings.sh:/cleanup-recordings.sh:ro
+      - /home/m/recordings:/recordings
+    command: ["/bin/sh", "/cleanup-recordings.sh"]