feat: gate GPU Service on Kubernetes cluster availability

GPU Service today only schedules on Kubernetes clusters; Docker / cloud
clusters can't host the CRDs. Without any awareness of that, Org
members whose Org has no K8s cluster (and no cluster_access grant on
one) saw a menu they couldn't use and a form that bottomed out with
backend errors.

Two changes lock the UX down:

- Boot probes the caller's cluster list once and stashes
  hasKubernetesCluster in initialState. A new canSeeGpuService
  predicate gates the menu — admins and Org owners always see it
  (they can add the cluster); everyone else only sees it when a
  reachable K8s cluster actually exists.

- The instances page filters its own cluster list to Kubernetes
  before deciding what to show. With nothing reachable we render the
  Deployments-style 'No clusters available. Add a Kubernetes cluster
  to get started.' empty state and hide the create-instance CTA;
  admins and Org owners additionally get the 'Add cluster' button
  that jumps to cluster management.

src/locales/ru-RU/no-result.ts

@@ -37,6 +37,8 @@ export default {
   'noresult.catalog.nofound': 'Подходящие модели не найдены.',
   'noresult.resources.cluster':
     'No clusters available. Add a cluster to get started.',
+  'noresult.resources.k8sCluster':
+    'No clusters available. Add a Kubernetes cluster to get started.',
   'noresult.resources.worker':
     'No workers available. Add a worker to get started.',
   'noresult.resources.gotocluster': 'Create Your First Cluster',
@@ -67,8 +69,7 @@ export default {
   'noresult.gpuservice.storage.subTitle': 'Хранилища ещё не добавлены.',
   'noresult.gpuservice.storage.nofound': 'Подходящие хранилища не найдены.',
   'noresult.gpuservice.storageType.title': 'Нет типов хранилищ',
-  'noresult.gpuservice.storageType.subTitle':
-    'Типы хранилищ ещё не добавлены.',
+  'noresult.gpuservice.storageType.subTitle': 'Типы хранилищ ещё не добавлены.',
   'noresult.gpuservice.storageType.nofound':
     'Подходящие типы хранилищ не найдены.',
   'noresult.gpuservice.sshkey.title': 'Нет открытых ключей SSH',