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/pages/_components/pie-chart/index.tsx

@@ -47,6 +47,10 @@ const PieChart: React.FC<PieChartProps> = ({
       color: colors,
       tooltip: {
         trigger: 'item',
+        // Keep the tooltip inside the chart box — the donut sits on the left, so
+        // a left-slice tooltip could otherwise spill out and get hidden behind
+        // the side menu.
+        confine: true,
         backgroundColor: token.colorBgElevated,
         borderColor: 'transparent',
         formatter: (params: any) => {
@@ -69,6 +73,9 @@ const PieChart: React.FC<PieChartProps> = ({
         itemWidth: 8,
         itemHeight: 8,
         itemGap: 10,
+        // Long names are truncated in the legend; hovering shows the full name
+        // in a tooltip.
+        tooltip: { show: true },
         textStyle: {
           color: token.colorTextTertiary,
           overflow: 'truncate',