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/components/system/useAuditSettings.ts

@@ -0,0 +1,89 @@
+// 审计策略配置 — 保留天数与应用后立即清理 // Logan.Li
+import { useState, useEffect, useCallback } from 'react';
+import { toast } from 'sonner';
+import { auditSettingsApi, type AuditSettings } from '@/api';
+
+const RETENTION_OPTIONS = [7, 15, 30, 90, 180, 365] as const;
+
+export function useAuditSettings() {
+  const [settings, setSettings] = useState<AuditSettings | null>(null);
+  const [retentionDays, setRetentionDays] = useState('180');
+  const [recordAll, setRecordAll] = useState(true);
+  const [loading, setLoading] = useState(true);
+  const [applying, setApplying] = useState(false);
+
+  const load = useCallback(async () => {
+    setLoading(true);
+    try {
+      const data = await auditSettingsApi.get();
+      setSettings(data);
+      setRetentionDays(String(data.retention_days || 180));
+      setRecordAll(data.record_all !== false);
+    } catch {
+      toast.error('加载审计设置失败');
+    } finally {
+      setLoading(false);
+    }
+  }, []);
+
+  useEffect(() => {
+    load();
+  }, [load]);
+
+  const handleApply = async () => {
+    const days = Number(retentionDays);
+    if (!RETENTION_OPTIONS.includes(days as (typeof RETENTION_OPTIONS)[number])) {
+      toast.error('请选择有效的保留天数');
+      return;
+    }
+    setApplying(true);
+    try {
+      const res = await auditSettingsApi.apply({ retention_days: days, record_all: recordAll });
+      setSettings({
+        retention_days: res.retention_days ?? days,
+        record_all: res.record_all ?? recordAll,
+        last_cleanup_at: res.last_cleanup_at,
+        last_cleanup_summary: res.last_cleanup_summary,
+      });
+      const total = res.cleanup?.total ?? 0;
+      toast.success(
+        total > 0
+          ? `已应用 ${days} 天保留策略，立即清理 ${total} 条超期记录`
+          : `已应用 ${days} 天保留策略，暂无超期记录需清理`,
+      );
+    } catch (e: unknown) {
+      toast.error(e instanceof Error ? e.message : '应用失败');
+    } finally {
+      setApplying(false);
+    }
+  };
+
+  const lastCleanupText = (() => {
+    if (!settings?.last_cleanup_at) return null;
+    const t = new Date(settings.last_cleanup_at).toLocaleString('zh-CN', { hour12: false });
+    let detail = '';
+    if (settings.last_cleanup_summary) {
+      try {
+        const s = JSON.parse(settings.last_cleanup_summary) as { total?: number };
+        if (typeof s.total === 'number') {
+          detail = s.total > 0 ? `，清理 ${s.total} 条` : '，无超期记录';
+        }
+      } catch {
+        // ignore
+      }
+    }
+    return `上次清理：${t}${detail}`;
+  })();
+
+  return {
+    retentionDays,
+    setRetentionDays,
+    recordAll,
+    setRecordAll,
+    loading,
+    applying,
+    handleApply,
+    lastCleanupText,
+    retentionOptions: settings?.allowed_retention_days ?? [...RETENTION_OPTIONS],
+  };
+}