feat(audit): F1+F2 告警静默规则标记完成 + 审计日志CSV导出实现

F1 告警静默规则 [done]:
- 后端 alert_silence.go: CRUD + Toggle (onetime/daily/weekly 三模式)
- 告警引擎 isSilenced 集成 (alert_engine.go)
- 前端 SilenceRuleTab + SilenceDialog
- 路由 /alerts/silences 已注册

F2 审计日志导出 [done]:
- 重写 ExportAuditLogs: 真正的 CSV 导出 (encoding/csv + UTF-8 BOM)
- 支持 module/action/username/startTime/endTime 筛选
- 导出限制 10000 条防溢出，自动记录审计日志
- JSON 格式向后兼容 (format=json)
- 前端 exportLogs 传递查询参数

同时包含累积的前期工作:
- 目录重构 internal/ -> controller/model/router (v0.55-v0.57)
- 后端分层架构 dto/repository/service/utils
- 审计模块全功能 (终端审计/操作审计/登录日志)
- asciicast v2 录制格式
- SFTP 文件浏览器
- StatStrip 紧凑统计条
- 在线会话自动刷新
- LiveMonitor WebSocket 诊断修复

验证: go build ✅ | npm run build ✅ | Docker 部署 ✅ | 10 回归端点 ✅ | CSV 导出 ✅ | 静默 CRUD ✅

frontend/src/components/cloud/CloudAccountManager.tsx

@@ -172,62 +172,6 @@ export function CloudAccountManager() {
         </div>
       </div>
 
-      {/* Stats */}
-      <div className="grid grid-cols-4 gap-4">
-        <Card className="bg-slate-800 border-slate-700">
-          <CardContent className="p-4">
-            <div className="flex items-center justify-between">
-              <div>
-                <p className="text-slate-400 text-sm">账号总数</p>
-                <p className="text-2xl font-bold text-slate-100 mt-1">{stats.total}</p>
-              </div>
-              <div className="w-10 h-10 rounded-lg bg-blue-500/20 flex items-center justify-center">
-                <Cloud className="h-5 w-5 text-blue-400" />
-              </div>
-            </div>
-          </CardContent>
-        </Card>
-        <Card className="bg-slate-800 border-slate-700">
-          <CardContent className="p-4">
-            <div className="flex items-center justify-between">
-              <div>
-                <p className="text-slate-400 text-sm">正常</p>
-                <p className="text-2xl font-bold text-green-400 mt-1">{stats.active}</p>
-              </div>
-              <div className="w-10 h-10 rounded-lg bg-green-500/20 flex items-center justify-center">
-                <CheckCircle2 className="h-5 w-5 text-green-400" />
-              </div>
-            </div>
-          </CardContent>
-        </Card>
-        <Card className="bg-slate-800 border-slate-700">
-          <CardContent className="p-4">
-            <div className="flex items-center justify-between">
-              <div>
-                <p className="text-slate-400 text-sm">已停用</p>
-                <p className="text-2xl font-bold text-slate-400 mt-1">{stats.inactive}</p>
-              </div>
-              <div className="w-10 h-10 rounded-lg bg-slate-500/20 flex items-center justify-center">
-                <XCircle className="h-5 w-5 text-slate-400" />
-              </div>
-            </div>
-          </CardContent>
-        </Card>
-        <Card className="bg-slate-800 border-slate-700">
-          <CardContent className="p-4">
-            <div className="flex items-center justify-between">
-              <div>
-                <p className="text-slate-400 text-sm">异常</p>
-                <p className="text-2xl font-bold text-red-400 mt-1">{stats.error}</p>
-              </div>
-              <div className="w-10 h-10 rounded-lg bg-red-500/20 flex items-center justify-center">
-                <Key className="h-5 w-5 text-red-400" />
-              </div>
-            </div>
-          </CardContent>
-        </Card>
-      </div>
-
       {/* Filters */}
       <div className="flex items-center gap-4">
         <div className="relative flex-1 max-w-md">