Add volume definitions to compose.yaml files for data persistence

## Description

Add volume definitions to compose.yaml files across integration guides to ensure data persists across container restarts.

## Context

Multiple compose.yaml files in the integration guides currently do not define volumes for data persistence. This means data is lost when containers are restarted or recreated.

## Affected Files

Based on PR #367, the following compose.yaml files should be reviewed and updated:
- docs/integrate/influxdb/compose.yaml
- docs/integrate/amqp/compose.yaml
- docs/integrate/collectd/compose.yaml
- docs/integrate/mongodb/compose.yaml
- docs/integrate/mqtt/compose.yaml
- docs/integrate/mysql/compose.yaml
- docs/integrate/opentelemetry/collector/compose.yaml
- docs/integrate/opentelemetry/telegraf/compose.yaml
- docs/integrate/oracle/compose.yaml
- docs/integrate/postgresql/compose.yaml
- docs/integrate/statsd/compose.yaml
- docs/integrate/telegraf/compose.yaml

## References

- PR: https://github.com/crate/cratedb-guide/pull/367
- Comment: https://github.com/crate/cratedb-guide/pull/367#discussion_r2406369546
- Requested by: @amotl

## Acceptance Criteria

- [ ] Add volume definitions to CrateDB services in compose.yaml files
- [ ] Add volume definitions to database services (PostgreSQL, MongoDB, Oracle, etc.) where applicable
- [ ] Ensure volumes are named appropriately and documented
- [ ] Test that data persists across container restarts