Mirror the Tokens trend: add a clearable "Group by" select to the
MetricChartCard so the GPU Instances chart can split by instance type /
instance / user, and Storage by storage / user. When grouped, the chart
fetches group_by=["date", "<dim>"] (the same list style as the token usage
API) and pivots into one stacked series per group (shared buildTrendSeries
util), with a legend; ungrouped stays a single series. group_by is now a
list across the resource breakdown client; group-by options reuse the
bottom-table dimensions (Users only when org-wide).
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.
