feat(dashboard): 最近请求缓存命中列 + 中文模式人民币计价 + 价格解析记忆化

- 最近请求表新增缓存命中率列（缓存读取/总输入）
- useCurrency：中文界面费用按最新 USD→CNY 汇率显示 ¥，英文保持 $（open.er-api.com，缓存 12h，失败兜底 7.2）
- match_price 记忆化缓存：O(记录数×5910) → O(模型种类×5910)，扫描从秒级降到百毫秒级
- 仪表盘右上角显示加载耗时/数据量（get_summary 往返埋点）；Rust 侧分段计时

src/components/dashboard/DailyBars.tsx

@@ -1,7 +1,8 @@
 import { useMemo, useState } from "react";
 import { createPortal } from "react-dom";
 import { useTranslation } from "../../i18n";
-import { fmtPct, fmtTokens, fmtUsd } from "../../lib/dashboard-format";
+import { useCurrency } from "../../hooks/useCurrency";
+import { fmtPct, fmtTokens } from "../../lib/dashboard-format";
 import type { DailyRow } from "../../types/dashboard";
 import { DailyDetailModal } from "./DailyDetailModal";
 
@@ -43,6 +44,7 @@ function shortModel(model: string): string {
 
 export function DailyBars({ daily, dimension, names, unknownProviderLabel }: DailyBarsProps) {
   const { t } = useTranslation();
+  const { money } = useCurrency();
   const [selected, setSelected] = useState<DailyRow | null>(null);
 
   const colorMap = useMemo(() => {
@@ -103,7 +105,7 @@ export function DailyBars({ daily, dimension, names, unknownProviderLabel }: Dai
 
           const tooltipLines = [
             d.date,
-            `${t("totalTokens")}: ${fmtTokens(d.totalTokens)} · ${fmtUsd(d.costUsd)} · ${t("colCacheHit")} ${fmtPct(d.cacheHitRate)}`,
+            `${t("totalTokens")}: ${fmtTokens(d.totalTokens)} · ${money(d.costUsd)} · ${t("colCacheHit")} ${fmtPct(d.cacheHitRate)}`,
             ...segments.map((s) => `${displayName(s.key)}: ${fmtTokens(s.tokens)}`),
             "",
             t("doubleClickHint"),