헬스체크 추가

backend/internal/repository/clickhouse_repo.go

@@ -79,3 +79,10 @@ func (r *ClickHouseRepository) Create(log *domain.AuditLog) error {
 		log.Details,
 	)
 }
+
+func (r *ClickHouseRepository) Ping(ctx context.Context) error {
+	if r.conn == nil {
+		return fmt.Errorf("clickhouse connection is nil")
+	}
+	return r.conn.Ping(ctx)
+}