refactor: 将 Markdown 编辑器中的摘要分割线图标从剪刀替换为垂直分割图标

src/lib/components/admin/MarkdownEditor.svelte

@@ -15,7 +15,7 @@
 		Italic,
 		Link,
 		List,
-		Scissors,
+		SquareSplitVertical,
 		Strikethrough
 	} from 'lucide-svelte';
 	import { addToast } from '$lib/stores/toast.svelte';
@@ -347,7 +347,7 @@
 			{/if}
 		</div>
 		<button type="button" class="md-btn" onclick={insertMore} title="插入摘要分割线">
-			<Scissors aria-hidden="true" />
+			<SquareSplitVertical aria-hidden="true" />
 		</button>
 	</div>