Feature: Query Log Volume API

The [Query log volume APIs](https://grafana.com/docs/loki/latest/reference/api/#query-log-volume) should be implemented to support Grafana 11.x flows. Since qryn is already able to produce log volume responses, this is hopefully a functionality aliasing exercise.

### API Endpoints

- `GET` `/loki/api/v1/index/volume`
- `GET` `/loki/api/v1/index/volume_range`