feat(i18n): Dashboard 页面内容国际化迁移 — 3 组件(Dashboard/DashboardCharts/DashboardRecent)硬编码中文改翻译键 + zh-CN/en-US 新增 dashboard.* 121 键(241 total)

- Dashboard.tsx: 标题/副标题/刷新/服务器按钮/StatStrip 7 标签/概览卡片标题 全部 t() 化
- DashboardCharts.tsx: 云成本概览/Top5资源使用/费用分布/月度趋势/环比标签 i18n(computeMonthChange 用 i18n.t 避开非组件上下文)
- DashboardRecent.tsx: 告警消息/证书到期/发布历史/服务器状态/集群状态 5 卡片全量 i18n
- zh-CN.json/en-US.json: dashboard 命名空间扩展 stat/alerts/certificates/releases/serversStatus/clusters/cost/topUsage/system 9 子分组
- 翻译键总数 120→241 (zh-CN/en-US 完全对齐)
- tsc -b=0, npm build=✓(19.01s), 17/17 集成测试通过, Docker healthy

frontend/src/locales/en-US.json

@@ -179,20 +179,95 @@
   },
   "dashboard": {
     "title": "Dashboard",
-    "serverStats": "Server Statistics",
-    "totalServers": "Total Servers",
-    "onlineServers": "Online Servers",
-    "k8sClusters": "K8s Clusters",
-    "runningPods": "Running Pods",
-    "todayAlerts": "Today's Alerts",
-    "recentAlerts": "Recent Alerts",
-    "recentPipelines": "Recent Pipelines",
-    "recentReleases": "Recent Releases",
-    "systemOverview": "System Overview",
-    "resourceUsage": "Resource Usage",
-    "cpuUsage": "CPU Usage",
-    "memoryUsage": "Memory Usage",
-    "diskUsage": "Disk Usage",
-    "quickActions": "Quick Actions"
+    "subtitle": "Real-time monitoring & operations overview",
+    "lastUpdated": "Last updated",
+    "refresh": "Refresh",
+    "refreshing": "Refreshing",
+    "servers": "Servers",
+    "stat": {
+      "servers": "Servers",
+      "running": "Running",
+      "k8sClusters": "K8s Clusters",
+      "healthyClusters": "Healthy",
+      "alerts": "Alerts",
+      "critical": "Critical",
+      "monthlyCost": "Monthly Cost"
+    },
+    "alerts": {
+      "title": "Alert Messages",
+      "description": "Recently triggered alert events",
+      "viewAll": "View All",
+      "empty": "No alert events",
+      "emptyHint": "All systems running normally"
+    },
+    "certificates": {
+      "title": "Certificate Expiry",
+      "description": "SSL certificate expiration monitoring",
+      "expiringSoon": "expiring soon",
+      "expiringIn30Days": "within 30 days",
+      "empty": "No certificate data",
+      "expireDate": "Expires",
+      "expired": "Expired",
+      "days": "days"
+    },
+    "releases": {
+      "title": "Release History",
+      "description": "Today's application release records",
+      "viewAll": "View All",
+      "empty": "No release records",
+      "success": "Success",
+      "failed": "Failed",
+      "deploying": "Deploying",
+      "rolledBack": "Rolled Back",
+      "building": "Building"
+    },
+    "serversStatus": {
+      "title": "Server Status",
+      "description": "Server running status distribution",
+      "viewAll": "View All",
+      "running": "Running",
+      "maintenance": "Maintenance",
+      "stopped": "Stopped",
+      "cpu": "CPU",
+      "memory": "Memory",
+      "empty": "No servers"
+    },
+    "clusters": {
+      "title": "Kubernetes Clusters",
+      "description": "Kubernetes cluster health status",
+      "viewAll": "View All",
+      "empty": "No cluster data",
+      "healthy": "Healthy",
+      "warning": "Warning",
+      "error": "Error",
+      "nodes": "Nodes",
+      "pods": "Pods",
+      "cpu": "CPU",
+      "memory": "Memory"
+    },
+    "cost": {
+      "title": "Cloud Cost Overview",
+      "description": "Monthly cloud platform expenses",
+      "distribution": "Cost Distribution",
+      "monthlyTrend": "Monthly Trend",
+      "noData": "No data",
+      "newCost": "New cost",
+      "flat": "Flat",
+      "vsLastMonth": "vs last month"
+    },
+    "topUsage": {
+      "title": "Top 5 Resource Usage",
+      "description": "Highest CPU, memory, and disk usage",
+      "cpu": "CPU",
+      "memory": "Memory",
+      "disk": "Disk"
+    },
+    "resourceUsage": {
+      "title": "Resource Usage Trend",
+      "description": "System resource usage over the last 24 hours",
+      "cpu": "CPU",
+      "memory": "Memory",
+      "disk": "Disk"
+    }
   }
 }