fix: show usage against ∞ when a workspace has no resource quota

[terrywu510]

Problem

On Overview → Quota usage, the CPU / RAM / GPU Memory gauges take both their
numerator and denominator from kube_resourcequota. When a workspace is set to
Unlimited, the Workspace CR carries no spec.resourceQuota.hard, so no
ResourceQuota is created for the namespace and the whole metric family is absent
— the used counter as well as hard. All three cards therefore rendered
"No data" and the tile appeared empty.

Change

• [cluster]/[workspace]/+layout.server.ts already fetches the Workspace to
  resolve spec.namespace; it now also returns quotaUnlimited
  (spec.resourceQuota.hard === undefined) — the same definition the workspace
  create/update forms use for their "Unlimited" checkbox. The flag is threaded
  through the overview page and the dashboard shell to the quota tile only.
• When unlimited, the tile queries pod-level usage instead of the quota:
  sum(kube_pod_container_resource_{requests,limits}{namespace,resource,unit} <LIVE_PODS>),
  reusing the existing LIVE_PODS helper (Pending|Running) so the numerator
  matches what a ResourceQuota would have counted, and stays consistent with the
  cluster analytics namespace commitment panels. GPU Memory already derived its
  numerator from pod containers, so that query is unchanged. The six
  kube_resourcequota queries are skipped entirely in this mode.
• Rendering: the arc keeps its shape with an empty track, the percentage is
  replaced by ∞, the sub-label reads <current usage> / ∞, and the hard total
  in each card header shows ∞. A failed usage query still falls back to the
  usual "No data" state.
• Workspaces with a quota keep their existing queries, conditions and layout
  unchanged. A resource that individually omits its hard entry also keeps
  today's behavior (GPU Memory still shows 0 / 0) — only a wholly unlimited
  workspace switches to the ∞ presentation.

Verification

• pnpm check (svelte-check): 0 errors, 0 warnings
• eslint / prettier: clean
• Manually verified in the dashboard against both an unlimited workspace and a
  workspace with a quota, on the Requests and Limits views.