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.
Align with gpustack backend commits 7b57cd3b (add route dimension to
usage breakdown) and 51fd25c8 (use model_route_id as models_called):
* group_by, filters, and BreakdownItem now use the `route` dimension;
`models` filter cascader is replaced with a flat `routes` selector
(routes have no provider/cluster grouping).
* Tab / group_by option / column header keep the user-facing "模型 / Model"
wording — only the underlying data dimension changed.
* Drop cluster_name / provider_type columns from the breakdown table;
drop api_keys_used column per design.
* Fix pre-existing excel export bug in use-export-table — string
dataIndex was lodash-joined char-by-char ("input_tokens" →
"i_n_p_u_t..."), array dataIndex was used as a flat key against nested
rows. Rebuilt around buildSheetMeta that emits a stable field key plus
a formatMap using _.get(row, path) for nested values. Sheet name kept
as `models` to match the visible column label.
