[Ticket]: Usage backend: model catalogue for the console Model filter

## Type

Feature

## Summary

The Overview Model select had exactly one hardcoded option (all) and is being deleted. Restore the filter only when a real model catalogue is queryable.

## Intent

Console UI/UX revamp epic: https://github.com/ADORSYS-GIS/converse-frontends/issues/368 — the console cuts every surface that fakes missing backend data; this ticket is the backend contract needed to restore the surface honestly.

## Acceptance Criteria

- Contract available over the authz-rpc / usage query path the console consumes.
- Console follow-up can render real values with no hardcoded nulls.

_Source of truth: https://github.com/ADORSYS-GIS/converse-frontends/issues/368_