refactor(i18n): U40 Monitor + Agent 子组件残余硬编码中文 i18n 补全 — 14 文件 ~50 处→0

- ContextSwitchCard: CTX/IRQ/次 → t()
- ProcessTable: agentWaitData/cpuUsagePercent → t()
- FDUsageCard: fdHandles → t()
- PortMonitorTab: 黑名单/白名单/策略配置/暂无端口数据 → t()
- PortPolicyDialog: 白名单全量上报/黑名单仅上报/端口列表/逗号分隔/白名单无需配置/已输入端口 → t()
- HostTimeRangePicker: 时间范围/自定义/取消/应用 → t()
- DualLineChart: 接收/发送 → t(), i18n.t→useTranslation hook
- ZoomableAreaChart: 暂无数据 → t()
- SiteResultsPanel: 选择任务/次/可用率/立即拨测/SSL证书预警/到期/剩余/阈值/天 → t()
- MiddlewareMonitor: Redis单机集群/上次更新/添加平台默认/暂无实例 → t()
- SiteMonitor: subtitle → t()
- SNMPMonitor: 标题/采集间隔/IP地址/OID模板/SNMP版本/确认/暂无设备/采集指标/暂无指标 → t()
- HealthProbeSection: TCP目标地址/TCP端口 → t()
- AgentAlerts: Agent告警/刷新/未恢复/已恢复/恢复/新建规则/创建第一条规则 → i18n.t()

新增 monitor.lbl 46 语义化翻译键 + agent.alerts 6 键
zh/en 7762→7814 对齐
tsc -b=0, npm build✓ (16.88s), ESLint=0/43/any=0, go build=0, 17/17 测试通过

frontend/src/locales/en-US.json

@@ -4377,7 +4377,53 @@
       "noProbeHint": "No health probes. Click \"{{action}}\" to create one.",
       "searchFields": "Search fields",
       "receiveSend": "RX {{rx}} · TX {{tx}}",
-      "currentFDUsage": "Current {{pct}}%"
+      "currentFDUsage": "Current {{pct}}%",
+      "ctxPerSec": "CTX switches/sec",
+      "irqPerSec": "IRQ interrupts/sec",
+      "times": "times",
+      "agentWaitData": "Agent v2.0+ required, waiting for data…",
+      "cpuUsagePercent": "CPU Usage(%)",
+      "fdHandles": "FD File Handles",
+      "blacklistLabel": "Blacklist",
+      "whitelistModeLabel": "Whitelist mode",
+      "policyConfig": "Policy Config",
+      "noPortData": "No port data",
+      "whitelistFullReport": "Whitelist — Report all",
+      "blacklistSelectedOnly": "Blacklist — Report selected only",
+      "portListLabel": "Port list",
+      "portListHint": "(comma-separated, e.g.: 80,443,3306,6379)",
+      "whitelistNoConfig": "— No config needed in whitelist mode",
+      "portsEntered": "{{count}} ports entered",
+      "timeRange": "Time range",
+      "custom": "Custom",
+      "apply": "Apply",
+      "rx": "RX",
+      "tx": "TX",
+      "noData": "No data",
+      "selectTaskHint": "Select a task to view protocol-specific metrics",
+      "probeNow": "Probe now",
+      "sslCertWarning": "SSL Certificate Warning",
+      "sslExpiring": "Expires",
+      "sslRemaining": "remaining",
+      "sslThreshold": "threshold",
+      "sslDays": "days",
+      "availabilityRate": "Availability",
+      "redisMysqlAutoRefresh": "Redis standalone/cluster · MySQL · 30s auto refresh",
+      "lastUpdate": "Last update",
+      "addPlatformDefault": "Add platform default",
+      "noInstancePrefix": "No",
+      "instanceSuffix": "instances",
+      "siteMonitorSubtitle": "HTTP Web probe · SSL cert detection · TCP / DNS / PING",
+      "snmpMonitorTitle": "SNMP Monitor",
+      "snmpCollectInterval": "5 min collection · 7 day retention",
+      "tcpTargetAddr": "TCP target address",
+      "tcpPort": "TCP port",
+      "ipAddress": "IP address",
+      "snmpOidTemplate": "OID Template",
+      "snmpVersion": "SNMP Version",
+      "snmpNoDevice": "No SNMP devices. Click \"Add Device\" to start monitoring.",
+      "snmpCollectMetrics": "Collected Metrics",
+      "snmpNoMetrics": "No metrics yet. Please collect first."
     },
     "logAlertBell": {
       "linked": "Alert Policy Linked",
@@ -7043,7 +7089,7 @@
       "loadFailed": "Failed to load alert data",
       "resolveAlert": "Resolve Alert",
       "resolveConfirm": "Mark this alert as resolved?",
-      "resolved": "Alert resolved",
+      "resolved": "Resolved",
       "deleteRule": "Delete Rule",
       "thresholdTriggered": "Alert threshold triggered",
       "noResolved": "No resolved alerts",
@@ -7051,7 +7097,12 @@
       "metricSwap": "Swap Usage",
       "metricLoad1": "1-min Load Average",
       "metricInode": "Inode Usage",
-      "metricTcpEst": "TCP Established"
+      "metricTcpEst": "TCP Established",
+      "title": "Agent Alerts",
+      "unresolved": "Unresolved",
+      "resolve": "Resolve",
+      "newRule": "New Rule",
+      "createFirstRule": "Create your first rule"
     },
     "allPortsHint": "All ports reported automatically",
     "allPortsMode": "All Ports",