[TASK] Implement "Create Volume" Modal

[jenny-s51]

Certification

• I certify I am an Epic Owner for Kubeflow Notebooks 2.0 and expected to create planning-related issues.

Description

As a Workspace user, Bella needs a simple way to create volumes to her Workspace k8s pods. Bella should be able to create new volumes without needing to understand underlying Kubernetes concepts.

This task involves creating a single, comprehensive modal that serves as the primary UI for creating volumes for a Workspace. The modal will be triggered by a "Create Volume" button in the Workspace properties section of the Workspace Form (within the Volumes subsection).

Acceptance Criteria

• Include PVC name, description, storage class (dropdown, options from List Storage Classes API), access mode (single selection: RWO, RWX, ROX, RWOP), persistent storage size with unit, and mount path.
  • Storage class, PVC name, and mount path are required.
• UX and patterns align with the existing Secrets flow in the Workspace Form
• Frontend validation on PVC name: disallow whitespace and special characters (e.g. allow only lowercase alphanumeric and hyphens).
• Access mode is immutable after creation.
  • UI should surface that it cannot be changed after creation (e.g. in-modal message or banner).
  • Help text (e.g. popover) should explain access mode in user-friendly terms and reflect the currently selected mode.

[thaorell]

/area frontend
/area v2

[thaorell]

/assign