Remove local data bind mount from cron service

All COT data (database and downloaded HTML files) is stored on the
cot_data Docker volume via DB_PATH=/data/cot.db. The ./data bind mount
was redundant and could leak local files into the container.

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

docker-compose.yml

@@ -24,7 +24,6 @@ services:
     container_name: cot_cron
     volumes:
       - cot_data:/data
-      - ./data:/app/data
     environment:
       - DB_PATH=/data/cot.db
     command: /app/scripts/cron_entrypoint.sh