refactor(i18n): U41 残余硬编码中文清零 — 工具函数+审计RDP标签+AIOps分析+Monitor残余+审批选项

18 文件 ~35 处 UI 硬编码中文→t()/i18n.t() 调用:
- agent-utils.ts timeAgo() 秒前/分钟前/小时前
- utils.ts formatDistanceToNow() 分钟前/小时前/天前
- request.ts 响应解析失败错误消息
- ActiveSessionsPanel/HistorySessionsPanel RDP 在线/历史会话标签
- MetricsExplorer 清除/已选/最近1小时
- HostMonitor 当前主机 subtitle
- AIAnalysisResult 证据链 (新增 useTranslation hook)
- capacity-predict.ts 容量预测摘要模板
- ApprovalResourcePage 阿里云/腾讯云/华为云
- ApprovalPermissionPage 堡垒机
- site-monitor/helpers.ts 频率/时间/证书天数格式化
- site-monitor/analytics.ts 证书剩余/检查失败/延迟波动事件
- middleware-monitor MwTargetChartsPanel/MwTrendChart/helpers.ts
- snmp-monitor SnmpMetricTrendChart/SnmpDeviceChartsPanel
- host-monitor/utils.ts 图表点数标签 + PortPolicyDialog 系统进程说明

新增 34 翻译键 (common.duration.secAgo/hourAgo/dayAgo + common.selected/
responseParseError/rdpActiveSessions/rdpHistorySessions/rdpSessionCount/
evidenceChain/last1Hour/currentHost + monitor.lbl 10键 + monitor.siteMonitor
8键 + approval.provider 3键 + approval.permType 1键 +
monitor.portPolicyDialog.systemProcessDesc + aiops.capacity.summary)

zh/en 7813→7847 对齐; tsc -b=0, npm build✓ (17.31s), ESLint=0/43/any=0,
go build=0, 17/17 测试通过

frontend/src/pages/monitor/middleware-monitor/MwTrendChart.tsx

@@ -1,5 +1,6 @@
 // 中间件指标趋势图 — 光标拖拽选区 // Logan.Li
 import { useMemo } from 'react';
+import i18n from '@/i18n';
 import {
   AreaChart, Area, XAxis, YAxis, CartesianGrid, Tooltip, ResponsiveContainer,
   ReferenceArea,
@@ -41,7 +42,7 @@ export function MwTrendChart({
   if (chartData.length === 0) {
     return (
       <div className="flex items-center justify-center text-xs text-[var(--dg-text-muted)]" style={{ height }}>
-        暂无趋势数据
+        {i18n.t('monitor.lbl.noTrendData')}
       </div>
     );
   }