docs(monitoring): Docker Desktop local-run notes (host-metrics profile)

monitoring/README.md

@@ -109,3 +109,16 @@ webhook uses it post-rebuild regardless of the metrics stack.
 - `GET /metrics` — Prometheus format (unauthenticated, for scraping).
 - JSON request logs with `X-Request-ID` (set `LOG_FORMAT=json` in prod)
   → shipped to Loki by Promtail.
+
+## Local runs (Docker Desktop)
+
+Start WITHOUT `--profile host-metrics` — node-exporter and cAdvisor need
+Linux rootfs mounts and will fail to start on Windows/macOS hosts:
+
+```bash
+docker compose -f monitoring/docker-compose.monitoring.yml --env-file .env up -d
+```
+
+Per-container and host metrics are absent locally; API metrics, Postgres
+metrics, logs, GlitchTip and Grafana all work the same. On the Linux VPS
+always include `--profile host-metrics`.