feat: 监控告警体系统一重构 + 自动化任务调度引擎 + 监控大屏拆分

告警中心
- 新增统一告警(alert_unified)、监控告警规则(monitor_alert_rule)、指标目录(alert_metric_catalog)
- 通知策略与消息分发(alert_notify_policy/dispatch/message)、静默规则
- 告警引擎按阈值/SNMP 拆分(alert_engine_monitor/snmp)

监控采集
- SNMP 常量/模板与历史指标(snmp templates/constants、snmp_metrics_history、snmp_collect)
- 中间件监控 Redis 采集与种子(middleware_monitor_redis/seed)
- 站点探测 pkg(siteprobe) + 站点视图(site_view)

自动化任务
- cron 调度器(cronscheduler)、脚本运行器(scriptrunner)、系统任务(systask)及运行记录(cron_job_run、system_task)

审计与凭证
- 审计设置(audit_setting) + 历史清理(auditcleaner)

前端
- 监控页面(host/middleware/site/snmp)拆分为子模块并大屏化
- 告警中心多 Tab(规则/指标目录/通知策略/静默)、任务管理组件重构、Agent CLI Markdown 渲染
- 移除旧脚本卡片/详情/日志组件，统一为 ScriptTable/ScriptCodeEditor/TerminalOutput

Co-Authored-By: Claude <noreply@anthropic.com>

frontend/src/pages/audit/AuditOperationsTab.tsx

@@ -1,6 +1,7 @@
 // 操作审计 Tab — 增强版审计日志列表，含筛选/导出/统计/清除
 // v2: 虚拟滚动渲染，支持万级日志流畅查看
 import { useState, useEffect, useCallback, useMemo, useRef } from 'react';
+import { cn } from '@/lib/utils';
 import { useTranslation } from 'react-i18next';
 import { useVirtualizer } from '@tanstack/react-virtual';
 import { Card, CardContent } from '@/components/ui/card';
@@ -66,7 +67,7 @@ export function AuditOperationsTab() {
     ...(actionFilter ? { action: actionFilter } : {}),
   }), [moduleFilter, actionFilter]);
 
-  const { data: auditData, isLoading: loading, refetch: refetchLogs } = useAuditLogs(auditParams);
+  const { data: auditData, isLoading: loading, isFetching, refetch: refetchLogs } = useAuditLogs(auditParams);
   const logs = useMemo(
     () => (auditData?.list || []).map((raw) => normalizeLog(raw)),
     [auditData],
@@ -219,8 +220,8 @@ export function AuditOperationsTab() {
       toolbar={toolbar}
       actions={(
         <>
-          <Button variant="outline" className="dg-btn-secondary" onClick={() => refetchLogs()}>
-            <RefreshCw className="h-4 w-4 mr-2" />{t('common.refresh')}
+          <Button variant="outline" className="dg-btn-secondary" onClick={() => refetchLogs()} disabled={isFetching}>
+            <RefreshCw className={cn('h-4 w-4 mr-2', isFetching && 'animate-spin')} />{t('common.refresh')}
           </Button>
           <Button variant="outline" className="dg-btn-secondary" onClick={handleExport}>
             <Download className="h-4 w-4 mr-2" />{t('common.export')}