Preview the live resources a project's cascade delete would destroy

Returns a preview of everything that currently lives inside a project, grouped into four fixed categories (compute, storage, network, other), so a confirmation UI can show exactly what a cascade delete of the project would destroy before the caller consents. Each category is always present in the response, in that fixed order, even when its count is 0 — the confirmation dialog renders one checkbox per category and depends on a stable category set to know how many consents exist. Each category carries up to 100 named items (kind, id, name); itemsTruncated is true when count exceeds the number of items returned, so a project holding thousands of volumes never produces an unbounded payload. name is always populated — for the floatingIp kind it carries the IP address, since floating IPs have no name column. Validation: scopeId must reference an accessible scope and projectId must reference a project visible in that scope; an unknown or out-of-scope project maps to NOT_FOUND (404). No body or mutation parameters exist. Async & state: Synchronous read; no state change — nothing is deleted, locked, or reserved by calling this endpoint. Errors: 401 when unauthenticated; 403 from any of three checks — the caller's role does not grant IAM read on the scope, a bearer API token is missing the iam:read action scope (token principals only, so even an owner's token gets 403 without it), or the caller is not an owner of the resource group (this preview carries the same authorization as the cascade delete it gates, so a contributor or reader who does hold IAM read still gets 403); 404 when the project does not exist or is not visible in this scope; 500 on read-model failure. Idempotency/Concurrency: Safe, cacheable; no idempotency key required.