refactor(usage): switch breakdown dimension from model to route

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.

src/pages/usage/hooks/use-models-columns.tsx

@@ -1,15 +1,10 @@
 // columns.ts
-import ProviderLogo from '@/pages/maas-provider/components/provider-logo';
 import { AutoTooltip } from '@gpustack/core-ui';
 import { useIntl } from '@umijs/max';
 import { Tag } from 'antd';
 import { useMemo } from 'react';
 import { BreakdownItem as ListItem } from '../config/types';
 
-interface ColumnsHookProps {
-  sortOrder: string[];
-}
-
 const useModelsColumns = (): Array<{
   title: string;
   dataIndex: string | string[];
@@ -21,8 +16,8 @@ const useModelsColumns = (): Array<{
     return [
       {
         title: intl.formatMessage({ id: 'common.table.name' }),
-        dataIndex: ['model', 'identity', 'value', 'model_name'],
-        key: 'model_name',
+        dataIndex: ['route', 'label'],
+        key: 'route_name',
         render: (text: string, record: ListItem) => (
           <span className="flex items-center">
             <AutoTooltip
@@ -32,7 +27,7 @@ const useModelsColumns = (): Array<{
             >
               <span className="text-primary">{text}</span>
             </AutoTooltip>
-            {record.model?.deleted && (
+            {record.route?.deleted && (
               <Tag
                 style={{
                   marginLeft: 8,
@@ -49,28 +44,6 @@ const useModelsColumns = (): Array<{
           </span>
         )
       },
-      {
-        title: intl.formatMessage({ id: 'usage.table.cluster' }),
-        dataIndex: ['model', 'identity', 'value', 'cluster_name'],
-        key: 'cluster_name',
-        render: (text: string, record: ListItem) => (
-          <AutoTooltip ghost>{text || '-'}</AutoTooltip>
-        )
-      },
-      {
-        title: intl.formatMessage({ id: 'usage.table.provider' }),
-        dataIndex: ['model', 'identity', 'value', 'provider_type'],
-        key: 'provider_type',
-        render: (text: string, record: ListItem) => (
-          <span className="flex-center gap-8">
-            <ProviderLogo provider={text || 'deployments'} />
-            <AutoTooltip ghost style={{ maxWidth: 400 }}>
-              {text ||
-                (!text && intl.formatMessage({ id: 'menu.models.deployment' }))}
-            </AutoTooltip>
-          </span>
-        )
-      },
       {
         title: intl.formatMessage({ id: 'usage.filter.inputTokens' }),
         dataIndex: 'input_tokens',