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/layout/Header.tsx

@@ -1,9 +1,8 @@
-import { useState, useCallback, useEffect, useRef } from 'react';
+import { useState, useCallback, useEffect } from 'react';
 import { useNavigate } from 'react-router-dom';
 import { cn } from '@/lib/utils';
 import { useThemeStore, useNotificationStore, useUserStore } from '@/store';
 import { Button } from '@/components/ui/button';
-import { Input } from '@/components/ui/input';
 import { Separator } from '@/components/ui/separator';
 import {
   DropdownMenu,
@@ -14,7 +13,6 @@ import {
   DropdownMenuTrigger,
 } from '@/components/ui/dropdown-menu';
 import {
-  Search,
   Bell,
   Menu,
   Settings,
@@ -30,30 +28,18 @@ import {
 import { formatDistanceToNow } from '@/lib/utils';
 import { useTheme, THEME_OPTIONS } from '@/hooks/useTheme';
 
-// Keyboard shortcut handler
+// Keyboard shortcut handler — Cmd/Ctrl+B 切换侧边栏
 function useKeyboardShortcuts() {
-  const _navigate = useNavigate();
-  const [searchOpen, setSearchOpen] = useState(false);
-
   useEffect(() => {
     const handler = (e: KeyboardEvent) => {
-      // Cmd/Ctrl + K to open search
-      if ((e.metaKey || e.ctrlKey) && e.key === 'k') {
-        e.preventDefault();
-        setSearchOpen((prev) => !prev);
-      }
-      // Cmd/Ctrl + B to toggle sidebar
       if ((e.metaKey || e.ctrlKey) && e.key === 'b') {
         e.preventDefault();
-        // Dispatch custom event for sidebar toggle
         window.dispatchEvent(new CustomEvent('toggle-sidebar'));
       }
     };
     window.addEventListener('keydown', handler);
     return () => window.removeEventListener('keydown', handler);
   }, []);
-
-  return { searchOpen, setSearchOpen };
 }
 
 export function Header() {
@@ -62,9 +48,6 @@ export function Header() {
   const { user, logout } = useUserStore();
   const { theme, setTheme } = useTheme();
   const navigate = useNavigate();
-  const [searchValue, setSearchValue] = useState('');
-  const [searchFocused, setSearchFocused] = useState(false);
-  const searchInputRef = useRef<HTMLInputElement>(null);
   useKeyboardShortcuts();
 
   const handleLogout = () => {
@@ -87,18 +70,6 @@ export function Header() {
     }
   }, []);
 
-  // Quick nav items for search
-  const quickNavItems = [
-    { name: '仪表盘', path: '/', icon: 'LayoutDashboard' },
-    { name: '服务器管理', path: '/servers', icon: 'Server' },
-    { name: 'Kubernetes 集群', path: '/kubernetes', icon: 'Cloud' },
-    { name: '监控告警', path: '/alerts', icon: 'Bell' },
-    { name: '告警中心', path: '/alert-center', icon: 'AlertTriangle' },
-    { name: '流水线', path: '/pipelines', icon: 'GitBranch' },
-    { name: '智能助手', path: '/ai-assistant', icon: 'Brain' },
-    { name: '脚本库', path: '/scripts', icon: 'FileCode' },
-  ];
-
   return (
     <header
       className={cn(
@@ -121,79 +92,6 @@ export function Header() {
           >
             <Menu className="h-4 w-4" />
           </Button>
-
-          {/* Global Search */}
-          <div className={cn(
-            'relative transition-all duration-300',
-            searchFocused ? 'w-[28rem] max-w-full' : 'w-80'
-          )}>
-            <Search className="absolute left-3 top-1/2 -translate-y-1/2 h-4 w-4 text-[var(--dg-text-muted)] pointer-events-none" />
-            <Input
-              ref={searchInputRef}
-              type="text"
-              placeholder="搜索服务器、应用、工单、文档..."
-              value={searchValue}
-              onChange={(e) => setSearchValue(e.target.value)}
-              onFocus={() => setSearchFocused(true)}
-              onBlur={() => setTimeout(() => setSearchFocused(false), 200)}
-              className={cn(
-                'pl-9 h-9 text-sm transition-all duration-300',
-                'bg-[var(--dg-bg-tertiary)] border-[var(--dg-border)]',
-                'text-[var(--dg-text-primary)] placeholder:text-[var(--dg-text-muted)]',
-                'focus:border-[var(--dg-blue)] focus:ring-1 focus:ring-[var(--dg-blue)]/30',
-                'hover:border-[var(--dg-border-hover)]',
-              )}
-            />
-            <kbd className="absolute right-3 top-1/2 -translate-y-1/2 px-1.5 py-0.5 text-[10px] font-mono text-[var(--dg-text-muted)] bg-[var(--dg-bg-primary)] border border-[var(--dg-border)] rounded hidden sm:inline-block">
-              ⌘K
-            </kbd>
-
-            {/* Search Dropdown */}
-            {searchFocused && searchValue && (
-              <div
-                className={cn(
-                  'absolute top-full left-0 right-0 mt-2 py-2 rounded-lg',
-                  'bg-[var(--dg-bg-secondary)] border border-[var(--dg-border)]',
-                  'shadow-lg z-50 animate-scale-in',
-                )}
-                style={{ boxShadow: 'var(--shadow-dropdown)' }}
-              >
-                <div className="px-3 py-1.5 text-xs font-medium text-[var(--dg-text-muted)] uppercase tracking-wider">
-                  快速导航
-                </div>
-                {quickNavItems
-                  .filter((item) =>
-                    item.name.toLowerCase().includes(searchValue.toLowerCase())
-                  )
-                  .map((item) => (
-                    <button
-                      key={item.path}
-                      className={cn(
-                        'w-full flex items-center gap-2.5 px-3 py-2 text-sm',
-                        'text-[var(--dg-text-secondary)] hover:text-[var(--dg-text-primary)]',
-                        'hover:bg-[var(--dg-bg-hover)] transition-colors text-left',
-                      )}
-                      onMouseDown={(e) => {
-                        e.preventDefault();
-                        navigate(item.path);
-                        setSearchValue('');
-                        setSearchFocused(false);
-                      }}
-                    >
-                      <Search className="h-3.5 w-3.5" />
-                      <span>{item.name}</span>
-                    </button>
-                  ))}
-                {quickNavItems.filter((item) =>
-                  item.name.toLowerCase().includes(searchValue.toLowerCase())
-                ).length === 0 && (
-                  <div className="px-3 py-4 text-center text-sm text-[var(--dg-text-muted)]">
-                    未找到匹配的结果
-                  </div>
-                )}
-              </div>
-            )}
-          </div>
         </div>
 
         {/* Right: Actions */}