feat(TopBar): 添加搜索功能组件并优化结构

- 新增 SearchInput、SearchDropdown、SearchResultItem 和 TopBarActions 组件，增强 TopBar 的搜索功能。
- 更新 useTopBar 钩子以支持最近搜索功能，并优化搜索历史管理。
- 修改 TopBar 组件以整合新组件，提升可读性和可维护性。
- 更新 README.md，反映新增组件和功能。

src/layout/TopBar/SearchResultItem.tsx

@@ -0,0 +1,34 @@
+import React from 'react';
+import { type FeatureConfig } from '@/config/features';
+import { cn } from '@/lib/utils';
+
+interface SearchResultItemProps {
+  feature: FeatureConfig;
+  selected: boolean;
+  onSelect: (feature: FeatureConfig) => void;
+}
+
+const SearchResultItem = React.memo(({ feature, selected, onSelect }: SearchResultItemProps) => {
+  return (
+    <li
+      role="option"
+      aria-selected={selected}
+      onClick={() => onSelect(feature)}
+      className={cn(
+        'flex cursor-pointer items-center gap-3 rounded-md px-3 py-2.5 text-sm transition-colors',
+        selected ? 'bg-accent text-accent-foreground' : 'hover:bg-muted/60',
+      )}
+    >
+      <div className="flex h-8 w-8 shrink-0 items-center justify-center rounded-lg bg-muted/80 text-muted-foreground">
+        {feature.icon && <feature.icon className="h-4 w-4" />}
+      </div>
+      <div className="min-w-0 flex-1">
+        <p className="truncate font-medium text-foreground">{feature.label}</p>
+        <p className="mt-0.5 truncate text-xs text-muted-foreground">{feature.description}</p>
+      </div>
+    </li>
+  );
+});
+SearchResultItem.displayName = 'SearchResultItem';
+
+export default SearchResultItem;