feat(i18n): ServerManager 服务器管理页国际化 — 27 处硬编码中文改翻译键 + server 命名空间(48 键)

- ServerManager.tsx: 页面标题/按钮/搜索/状态筛选/表头/分页/toast/CSV导出/确认弹框 全量 t() 化
- 复用 common.* 通用键(refresh/export/delete/status/actions/loading/running/stopped/maintenance/offline)
- 新增 server.* 命名空间: title/subtitle/batchImport/cloudImport/csvImport/addServer/searchPlaceholder/tableHeaders/pagination/toast/csv 子组
- zh-CN/en-US 键总数 242→290 (server 48 键, 中英完全对齐)
- tsc -b=0, npm build=✓(19.13s), 17/17 集成测试通过

frontend/src/locales/en-US.json

@@ -269,5 +269,53 @@
       "memory": "Memory",
       "disk": "Disk"
     }
+  },
+  "server": {
+    "title": "Server Management",
+    "subtitle": "Manage cloud platform server assets",
+    "batchImport": "Batch Import",
+    "importMethod": "Select import method",
+    "cloudImport": "Cloud Server Import",
+    "cloudImportHint": "Sync from cloud platform",
+    "csvImport": "CSV Import",
+    "csvImportHint": "hostname + IP only",
+    "addServer": "Add Server",
+    "searchPlaceholder": "Search hostname or IP...",
+    "allStatus": "All Status",
+    "hostname": "Hostname",
+    "ipAddress": "IP Address",
+    "publicIp": "Public IP",
+    "config": "Config",
+    "usage": "Usage",
+    "tags": "Tags",
+    "noData": "No server data",
+    "selected": "{{count}} selected",
+    "batchDelete": "Batch Delete",
+    "perPage": "per page",
+    "items": "items",
+    "totalItems": "{{count}} total",
+    "deleteTitle": "Delete Server",
+    "deleted": "Server deleted",
+    "batchDeleteTitle": "Batch Delete Servers",
+    "updated": "Server updated",
+    "created": "Server created",
+    "saveFailed": "Save failed, please retry",
+    "noExportData": "No data to export",
+    "exported": "Exported {{count}} servers",
+    "deletedCount": "Deleted {{count}} servers",
+    "deleteFailed": "Delete failed",
+    "batchDeleteFailed": "Batch delete failed",
+    "csv": {
+      "hostname": "Hostname",
+      "ip": "IP Address",
+      "publicIp": "Public IP",
+      "port": "Port",
+      "os": "OS",
+      "cpu": "CPU(Cores)",
+      "memory": "Memory(GB)",
+      "disk": "Disk(GB)",
+      "status": "Status",
+      "tags": "Tags"
+    }
   }
 }