As a Kessel API Consumer, I want the Workspace Creation endpoint to return a detailed, machine-readable error when the organization limit is reached, so that I understand why the request failed and how to resolve it without contacting support manually.

Acceptance Criteria

• Trigger: When a POST /workspaces request is made for an Org where count(standard_workspaces) >= WORKSPACE_ORG_CREATION_LIMIT.
• Updated error message: The response body must include the following error message: "Workspace limit reached (120/120); please free up capacity by deleting empty workspaces or consolidating those with similar users and role bindings."