refactor(i18n): U24 Monitor 模块 i18n hook 迁移 — 26 个 .tsx 文件从全局 i18n.t() 迁移到 useTranslation() hook + 89 个 phantom 中文文本键替换为 monitor.lbl.* 语义化键

- 新增 monitor.lbl 翻译子命名空间 89 键（HostMonitor/Middleware/Site/SNMP/Shared）
- 26 .tsx: import i18n → useTranslation() hook + i18n.t('中文') → t('monitor.lbl.semanticKey')
- 模块级代码(TABS/METRIC_CATEGORIES)保留 i18n.t() + 语义化键
- 1 .ts helpers 文件 phantom 键替换
- zh/en 6886→6975 +89 键对齐
- tsc -b=0, npm build✓ (17.16s), ESLint=0/53/0, go build=0, Docker healthy

frontend/src/pages/monitor/host-monitor/ZoomableAreaChart.tsx

@@ -13,7 +13,7 @@ import {
 import { ChartToolbar } from './ChartToolbar';
 import { MonitorChartTooltip } from '../shared/monitorChartTheme';
 import { ChartRangeHint } from '../shared/ChartRangeHint';
-import i18n from '@/i18n';
+import { useTranslation } from 'react-i18next';
 
 export interface ChartSeries {
   dataKey: string;
@@ -192,6 +192,7 @@ export const ZoomableAreaChart = forwardRef<ZoomableChartHandle, Props>(function
   onZoomedChange,
   referenceLines,
 }, ref) {
+  const { t } = useTranslation();
   const uid = useId().replace(/:/g, '');
   const gradPrefix = `grad-${chartId}-${uid}`;
 
@@ -316,11 +317,11 @@ export const ZoomableAreaChart = forwardRef<ZoomableChartHandle, Props>(function
         <DialogContent className={dialogClass}>
           <DialogHeader className="shrink-0 flex-row items-start justify-between gap-4 space-y-0 pr-10">
             <div className="min-w-0">
-              <DialogTitle className="text-base truncate">{title || i18n.t('指标详情')}</DialogTitle>
+              <DialogTitle className="text-base truncate">{title || t('monitor.lbl.metricDetail')}</DialogTitle>
               {subtitle && (
                 <p className="text-xs dg-text-muted mt-0.5 truncate">{subtitle}</p>
               )}
-              <DialogDescription className="sr-only"> {i18n.t('选择主机...')} </DialogDescription>
+              <DialogDescription className="sr-only"> {t('monitor.lbl.selectHost')} </DialogDescription>
             </div>
             <ChartToolbar
               size="md"