List and query VM snapshots in the active scope

Returns the VM snapshots visible in the active tenant/subscription/project scope, as rendered by the Snapshots page table. This single collection endpoint serves BOTH the plain route-load list and the search/filter/sort/pagination controls: free-text q matches snapshot name and source (instance or volume) name; the UI's quick-filter chips map to the status query parameter (Available / Creating); the table sorts on name, sizeGb and createdAt via sort+order. No resource state is mutated by this call. Validation: scopeId must resolve to a scope the caller can read or the request fails with 403 FORBIDDEN; a non-enum status value, unknown sort fields or out-of-range page/pageSize map to 422 VALIDATION_ERROR. Soft-deleted snapshots are always excluded (deleted_at IS NULL). Async & state: Synchronous read; no state change. In-flight captures surface as CREATING rows and their completion (AVAILABLE) or failure (ERROR) arrives as resource.updated SSE frames keyed by snapshot id with a patch on status/usedGb. Errors: 401 when the session is missing or expired; 403 when the caller lacks reader access to the scope; 422 on malformed query parameters; 500 on backend read-model failure. Idempotency/Concurrency: Safe, cacheable; no idempotency key required. Pagination is stable per meta so repeated identical reads return consistent pages.