Update User Manager to trigger USERSESSION cleanup on deletion

[offtherailz]

Description

Ensure that user deletion triggers the automated cleanup of sessions via the new backend parameter. See parent issue.

Proposed Changes

API Integration

• Update the User Manager epics/actions to append the cascadeDelete=USERSESSION parameter to the DELETE request.

UI/UX

• The user deletion flow remains unchanged (minimal complexity).
• The confirmation modal should remain simple

Checklist

• Update API call in User Manager epics.
• Verify that the deletion works correctly even if the backend returns no resources to clean.
• Ensure no regressions in the standard user deletion flow.