Add storage configuration

[adwk67]

Came up in https://stackable-workspace.slack.com/archives/C08GM6S8Z8D/p1765443130036129

CPU and memory can be configured for Airflow roles, but there is not anything implemented for storage: see https://github.com/stackabletech/airflow-operator/blob/main/rust/operator-binary/src/crd/mod.rs#L869.

This is at least partly due to the fact that Airflow data will typically either be held in the database, on log volumes (which have their own resources), or in a gitsync container., but it should be added to be consistent with other products.

The kind of things that would be supported can be seen in the HDFS config - PVCs backed by these storage types.

[sbernauer]

Correct me if I'm wrong, but an empty AirflowStorageConfig looks correct to me.
Airflow does not store any state on disk, there is no need for any PVCs. All state is stored on the postgres.

Relevant CRD section:

airflow-operator/deploy/helm/airflow-operator/crds/crds.yaml

Lines 232 to 233 in de3fe48

	storage:
	type: object

[lfrancke]

During planning we were a bit confused what the exact use-case for this is. We want to do a refinement first to understand what the use-case is and what is needed to solve it because storage might be one solution but there might be others.