feat(monitoring): add Kafka monitoring via kafka-exporter

- Add kafka-exporter service to docker-compose.yml
- Add kafka job to prometheus.yml scrape configs
- Add Kafka Overview dashboard (Grafana provisioning)
- Add Kafka alert rules (broker down, consumer lag, etc.)
- Add make reload-monitoring command for easy updates
- Update OPERATIONS.md with TL;DR and troubleshooting

API verified via Context7:
- /danielqsj/kafka_exporter for exporter config
- /prometheus/docs for scrape_configs format

docker-compose.yml

@@ -231,6 +231,18 @@ services:
       timeout: 10s
       retries: 5
 
+  # Kafka Exporter для мониторинга через Prometheus
+  kafka-exporter:
+    image: danielqsj/kafka-exporter:latest
+    command: ["--kafka.server=kafka:29092"]
+    ports:
+      - "9308:9308"
+    networks:
+      - cs_dwh
+    depends_on:
+      - kafka
+    restart: unless-stopped
+
 networks:
   cs_dwh:
     driver: bridge