Switch journal Docker health check from `node -e "fetch(...)"` to `curl -sf`,
matching the planner. The Node.js process spawn was heavy and prone to timeout
under memory pressure, causing false health check failures and 502s.
Upgrade Promtail from static file scraping to Docker service discovery so logs
get `service` and `container` labels. Parse Pino JSON logs to extract the
`level` label, enabling Loki queries filtered by log level.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Loki was running but had no log shipper — no labels or logs were
visible in Grafana. Adds Promtail to scrape all Docker container
logs and push them to Loki.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
