Captures the async-queue redesign of the PO/DN import pipeline (see
spec + plan) and rewrites the n8n implementation doc to match the
new cron-driven architecture (workflow 005iI4jX5mq9DsTR). Also
gitignores cooler.env so the local-only deployment reference is no
longer tracked.
Co-Authored-By: Claude <noreply@anthropic.com>