Backfill deep trade history (and cancel a runaway)

Trades are cursor-paginated and drain the whole window — a day of a liquid pair is millions of rows. Give an explicit start date:

dccd backfill -e okx -s BTC/USDT -t trades --start 2024-01-01

From the web UI, the Historical page shows the run’s live progress on the dataset’s coverage bar, and Run turns into Stop to cancel it (everything already collected is kept). Via the API:

curl -XDELETE localhost:8080/api/backfill/$RUN_ID