feat(usage): resource usage metering page

Add the Usage page with Summary / Tokens / GPU Instances / Storage / Resource
Events tabs over the new metering endpoints: per-resource breakdowns with
date / scope / user / resource filters, trend charts, server-side sortable
tables (GPU-Hours, Instance-Hours, GB-Days, GB-Hours), Excel export with an
in-dialog preview, and KPI cards with help tooltips explaining each metric.

MaaS-only users (no Kubernetes cluster and no resource events) get a
tokens-only view with the tab bar dropped; GPU Service / the full page unlock
for admins, cluster owners, or anyone who has run a resource. Instance-type
rows reuse the GPU Instances list styling, and deleted users / instances /
volumes are flagged in breakdowns and filters.

src/app.tsx

@@ -5,6 +5,7 @@ import { DEFAULT_ENTER_PAGE, GPUSTACK_API_BASE_URL } from '@/config/settings';
 import { COLOR_PRIMARY } from '@/config/theme/constants';
 import { queryClusterList } from '@/pages/cluster-management/apis';
 import { ProviderValueMap } from '@/pages/cluster-management/config';
+import { queryResourceEvents } from '@/pages/usage/apis/resource';
 import { enterprisePluginReady } from '@/plugins/enterprise-ready';
 import { GPUStackPluginManager } from '@/plugins/manager';
 import { requestConfig } from '@/request-config';
@@ -72,12 +73,44 @@ const probeHasKubernetesCluster = async (): Promise<boolean | undefined> => {
   }
 };
 
+// Probes whether the caller has ANY resource-usage events (GPU/CPU instance or
+// storage lifecycle). Used alongside the cluster probe so a user who has run
+// GPU instances still sees GPU Service / the full Usage page even if they
+// currently have no Kubernetes cluster. Mirrored into sessionStorage for the
+// access extensions; any failure → undefined ("unknown — don't restrict").
+const HAS_RESOURCE_EVENTS_KEY = 'hasResourceEvents';
+const probeHasResourceEvents = async (): Promise<boolean | undefined> => {
+  try {
+    // No date range = "ever"; scope is clamped to the caller server-side.
+    const res = await queryResourceEvents({ perPage: 1 });
+    const value = (res?.pagination?.total ?? 0) > 0;
+    try {
+      window.sessionStorage.setItem(
+        HAS_RESOURCE_EVENTS_KEY,
+        JSON.stringify(value)
+      );
+    } catch {
+      // sessionStorage may be unavailable; predicate treats missing as unknown.
+    }
+    return value;
+  } catch (error) {
+    console.error('probeHasResourceEvents error', error);
+    try {
+      window.sessionStorage.removeItem(HAS_RESOURCE_EVENTS_KEY);
+    } catch {
+      // ignore
+    }
+    return undefined;
+  }
+};
+
 // runtime configuration
 export async function getInitialState(): Promise<{
   fetchUserInfo: () => Promise<Global.UserInfo>;
   currentUser?: Global.UserInfo;
   pluginData?: Record<string, any>;
   hasKubernetesCluster?: boolean;
+  hasResourceEvents?: boolean;
 }> {
   const { location } = history;
 
@@ -161,16 +194,19 @@ export async function getInitialState(): Promise<{
   getAppVersionInfo();
 
   if (![DEFAULT_ENTER_PAGE.login].includes(location.pathname)) {
-    const [userInfo, hasKubernetesCluster] = await Promise.all([
-      fetchUserInfo(),
-      probeHasKubernetesCluster()
-    ]);
+    const [userInfo, hasKubernetesCluster, hasResourceEvents] =
+      await Promise.all([
+        fetchUserInfo(),
+        probeHasKubernetesCluster(),
+        probeHasResourceEvents()
+      ]);
     checkDefaultPage(userInfo);
     return {
       fetchUserInfo,
       currentUser: userInfo,
       pluginData,
-      hasKubernetesCluster
+      hasKubernetesCluster,
+      hasResourceEvents
     };
   }
   return {