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

Makefile

@@ -1,4 +1,4 @@
-.PHONY: up ddl data transform
+.PHONY: up ddl data transform reload-monitoring
 
 COMPOSE ?= docker compose
 
@@ -13,3 +13,16 @@ data:
 
 transform:
 	bash ./scripts/run_batch.sh
+
+# Перезагрузка конфигурации мониторинга (после изменений в provisioning)
+reload-monitoring:
+	@echo "=== Перезагрузка сервисов мониторинга ==="
+	$(COMPOSE) up -d prometheus grafana kafka-exporter
+	$(COMPOSE) restart prometheus
+	@echo "=== Перезагрузка provisioning Grafana ==="
+	@sleep 2
+	@curl -s -u admin:admin -X POST http://localhost:3000/api/admin/provisioning/datasources/reload && echo " [datasources]"
+	@curl -s -u admin:admin -X POST http://localhost:3000/api/admin/provisioning/dashboards/reload && echo " [dashboards]"
+	@curl -s -u admin:admin -X POST http://localhost:3000/api/admin/provisioning/alerting/reload && echo " [alerting]"
+	@echo "=== Проверка ==="
+	@curl -s http://localhost:9090/api/v1/targets | grep -o '"job":"[^"]*"' | sort | uniq