CRON_SECRET was required (min 32 chars) in production by env.js, but
neither docker-compose.yml nor docker-compose.coolify.yml passed it
through. Since the release container isn't covered by
SKIP_ENV_VALIDATION (build-stage only), bun run start failed env
validation on every docker deploy unless CRON_SECRET was manually
configured — even though it only gates the optional recurring-invoice
cron endpoint, which already handles being unset gracefully.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>