WP-12: Kubernetes overview and workload actions

kube-rs gateway (nodes, namespaces, deployments/statefulsets/daemonsets with
images, PVCs; rollout restart, scale, set image via patches) using the
microk8s kubeconfig by default, fake gateway for dev, /api/cluster routes,
Kubernetes page with node cards, workload table with admin actions and PVC
list. Also implements the streaming command runner that WP-11 relied on.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

frontend/e2e/cluster.spec.ts

@@ -10,7 +10,7 @@ test('cluster page shows node, workloads and lets an admin restart a workload',
   await page.getByRole('link', { name: 'Kubernetes' }).click()
 
   await expect(page.getByTestId('node-version')).toContainText('v1.32')
-  const row = page.getByRole('row', { name: /gitea-postgresql/ })
+  const row = page.getByRole('row', { name: /^gitea gitea-postgresql statefulset/ })
   await expect(row).toContainText('statefulset')
   page.once('dialog', (d) => d.accept())
   await page