Add cron schedules and sync docs

deploy/prometheus/README.md

@@ -1,9 +1,20 @@
 # Prometheus
 
-Placeholder for Prometheus examples.
+Example scrape configuration for the optional observability profile in
+`deploy/docker-compose.yml`.
 
-Planned examples:
+Run it with:
 
-- scrape Monlet agent `/metrics`;
-- scrape Monlet server `/metrics`;
-- sample rules for checks that use `notifications_enabled = false`.
+```sh
+cd deploy
+MONLET_AUTH_TOKEN=$(openssl rand -hex 16) docker compose --profile observability up
+```
+
+The example config scrapes:
+
+- `server:8000/metrics` as `monlet-server`
+- `host.docker.internal:9100/metrics` as `monlet-agent`
+
+Adjust the agent target for your environment. In the showcase stack one demo
+agent exposes metrics on host port `9465`; production agents usually expose
+`metrics.listen` only on the host or a private monitoring network.