refactor(i18n): U37 全量 JSX 文本节点硬编码中文清零 — 65 文件 151 处→0, 新增 common.* 98 翻译键, zh/en 对齐, tsc -b=0, npm build✓ (17.96s), ESLint=0/43/any=0, go build=0, 17/17 测试通过

frontend/src/components/monitor/AlertRulesTab.tsx

@@ -107,7 +107,7 @@ export function AlertRulesTab({
       {/* 批量操作栏 // Logan.Li */}
       {selectedIds.length > 0 && (
         <div className="flex items-center gap-2 mb-3">
-          <span className="text-sm dg-text-secondary">已选择 {selectedIds.length} 项</span>
+          <span className="text-sm dg-text-secondary">{i18n.t('common.selectedCount', { count: selectedIds.length })}</span>
           <Button
             variant="outline"
             size="sm"