feat(frontend): 控制台 next-intl 中英双语

接入无 URL 前缀的 zh-CN/en，顶栏与外观设置可切换语言；选择写入 cookie 后刷新生效。

frontend/app/(main)/nodes/components/network-trend-chart.tsx

@@ -1,5 +1,7 @@
 'use client';
 
+import { useTranslations } from 'next-intl';
+
 import { TrendChart } from '@/components/data/trend-chart';
 import {
   Card,
@@ -17,18 +19,23 @@ import {
 
 export function NetworkTrendChart({
   points,
-  title = '24 小时网络趋势',
-  description = '按小时展示已提供/接收数据（访问日志）；摘要为近 24 小时总量。',
+  title,
+  description,
 }: {
   points: NetworkTrendPoint[];
   title?: string;
   description?: string;
 }) {
+  const t = useTranslations('nodes.networkTrend');
   return (
     <Card className='border-dashed shadow-none'>
       <CardHeader>
-        <CardTitle className='text-sm font-semibold'>{title}</CardTitle>
-        <CardDescription className='text-xs'>{description}</CardDescription>
+        <CardTitle className='text-sm font-semibold'>
+          {title ?? t('title')}
+        </CardTitle>
+        <CardDescription className='text-xs'>
+          {description ?? t('description')}
+        </CardDescription>
       </CardHeader>
       <CardContent>
         <TrendChart
@@ -36,11 +43,11 @@ export function NetworkTrendChart({
             formatTrendHour(point.bucket_started_at),
           )}
           summaryScope='total'
-          summaryHint='近 24 小时'
+          summaryHint={t('summaryHint')}
           yAxisValueFormatter={formatBytes}
           series={[
             {
-              label: '接收数据',
+              label: t('received'),
               color: '#22c55e',
               fillColor: 'rgba(34, 197, 94, 0.14)',
               variant: 'area',
@@ -48,7 +55,7 @@ export function NetworkTrendChart({
               valueFormatter: formatBytes,
             },
             {
-              label: '已提供数据',
+              label: t('provided'),
               color: '#38bdf8',
               values: points.map((point) => point.bytes_provided),
               valueFormatter: formatBytes,