refactor(dashboard): collapse usage section into a single row

Merge the two "by Model" pies (Token Usage + API Requests) into one
dual-pie card with a shared right-side vertical legend and per-donut
center totals, drop the standalone API-Key Top 10 chart, and put the
combined chart side-by-side with the User Top 10 ranking in one row
with the same 16/8 column ratio used by the System Load section above.

* New component usage-charts/usage-by-model.tsx owns both metric queries
  (group_by=['date','route']), aggregates a shared route→color map so
  the legend toggles both donuts together, and renders two pies at
  centers ('20%','50%') and ('60%','50%') with radius ['50%','70%'].
* new-usage.tsx no longer mounts ApiRequestsByModel / TokenUsageByModel
  / TopTokenUsageByApiKey; layout collapses to two columns sized
  (lg=24 xl=16) and (lg=24 xl=8).
* Delete unused token-usage-by-model.tsx, api-requests-by-model.tsx,
  top-token-usage-by-api-key.tsx, and the use-top-token-usage-by-api-key
  hook.
* Strip the now-unreferenced dashboard.tokenUsageByModel /
  apiRequestsByModel / topTokenUsageByApiKey locale keys across 5
  locales, add the new dashboard.usageByModel title; locale parity
  check passes.

src/pages/dashboard/hooks/use-top-token-usage-by-api-key.ts

@@ -1,52 +0,0 @@
-import useQueryTimeSeriesData from '@/pages/usage/services/use-query-timeseries-data';
-import { useIntl } from '@umijs/max';
-import { useEffect, useMemo } from 'react';
-import {
-  baseColorMap,
-  DashboardUsageCommonParams,
-  toUsageRankData
-} from '../config';
-
-export default function useTopTokenUsageByApiKey(
-  commonParams: DashboardUsageCommonParams
-) {
-  const intl = useIntl();
-  const query = useQueryTimeSeriesData({
-    key: 'topTokenUsageByApiKeyData'
-  });
-  const tokenUsageText = intl.formatMessage({ id: 'dashboard.tokens' });
-
-  useEffect(() => {
-    query
-      .fetchData({
-        ...commonParams,
-        metric: 'total_tokens',
-        group_by: ['date', 'api_key'],
-        page: 1,
-        perPage: 10,
-        sort_by: '-total_tokens'
-      })
-      .catch(() => {});
-  }, [commonParams]);
-
-  const rankData = useMemo(() => {
-    const data = toUsageRankData(
-      query.detailData,
-      'api_key',
-      tokenUsageText,
-      baseColorMap.baseR3
-    );
-    return {
-      names: data.names.filter((name) => name !== '-'),
-      series: data.series.map((item) => ({
-        ...item,
-        data: item.data.filter((point) => point.name !== '-')
-      }))
-    };
-  }, [query.detailData, tokenUsageText]);
-
-  return {
-    rankData,
-    loading: query.loading
-  };
-}