feat(monitoring): add Airflow monitoring via statsd-exporter

- Add statsd-exporter service to docker-compose.yml (prom/statsd-exporter:v0.27.1)
- Add StatsD env vars to airflow-default-env for metrics export
- Add airflow job to prometheus.yml scrape configs
- Add Airflow Overview dashboard (Grafana provisioning)
- Add Airflow alert rules: scheduler down, queue backlog, failures, parse time
- Add configs/statsd_mapping.yml for StatsD → Prometheus conversion
- Use Prometheus naming convention (_total for counters, _seconds for timers)
- Add monitoring plan at plans/monitoring_airflow_plan.md
- Update OPERATIONS.md and Makefile for airflow monitoring

Tested: all 3 jobs (airflow, clickhouse, kafka) showing UP in Prometheus,
metrics flowing (dagbag_size=3, executor slots, heartbeats with _total suffix),
all 4 alert rules loaded in Grafana

docker-compose.yml

@@ -5,6 +5,11 @@ x-airflow-env: &airflow-default-env
   AIRFLOW__WEBSERVER__SECRET_KEY: ${AIRFLOW_SECRET_KEY:-replace-me-with-random-string}
   # ClickHouse connection для ETL
   AIRFLOW_CONN_CLICKHOUSE_DEFAULT: clickhouse://default:123456@clickhouse:9000/default
+  # StatsD для мониторинга (метрики → statsd-exporter → Prometheus)
+  AIRFLOW__METRICS__STATSD_ON: "True"
+  AIRFLOW__METRICS__STATSD_HOST: "statsd-exporter"
+  AIRFLOW__METRICS__STATSD_PORT: "8125"
+  AIRFLOW__METRICS__STATSD_PREFIX: "airflow"
 
 
 services:
@@ -242,6 +247,24 @@ services:
       - kafka
     restart: unless-stopped
 
+  # StatsD Exporter для Airflow метрик (StatsD → Prometheus)
+  statsd-exporter:
+    image: prom/statsd-exporter:v0.27.1
+    command: [
+      "--statsd.listen-udp=:8125",
+      "--statsd.listen-tcp=",
+      "--web.listen-address=:9102",
+      "--statsd.mapping-config=/tmp/statsd_mapping.yml"
+    ]
+    ports:
+      - "9102:9102"     # Prometheus metrics endpoint
+      - "8125:8125/udp" # StatsD receive port
+    volumes:
+      - ./configs/statsd_mapping.yml:/tmp/statsd_mapping.yml:ro
+    networks:
+      - cs_dwh
+    restart: unless-stopped
+
 networks:
   cs_dwh:
     driver: bridge