新增内容库每页数量选择功能

- 添加每页数量选择下拉框（20/50/100/200/500条）
- 默认100条，用户可自由选择

static/css/library.css

@@ -102,6 +102,15 @@
     cursor: pointer;
 }
 
+.page-size-select {
+    padding: 10px 15px;
+    border: 1px solid #ddd;
+    border-radius: 6px;
+    font-size: 14px;
+    background: white;
+    cursor: pointer;
+}
+
 .toolbar-right {
     display: flex;
     gap: 10px;

static/js/library.js

@@ -4,7 +4,7 @@ const API_BASE = '';
 // 状态
 let articles = [];
 let currentPage = 1;
-let pageSize = 100;  // 增加每页数量
+let pageSize = 100;
 let totalCount = 0;
 let selectedIds = new Set();
 let currentArticleId = null;
@@ -31,6 +31,13 @@ document.addEventListener('DOMContentLoaded', () => {
     });
 });
 
+// 改变每页数量
+function changePageSize() {
+    pageSize = parseInt(document.getElementById('page-size').value);
+    currentPage = 1;
+    loadArticles();
+}
+
 // 加载文章列表
 async function loadArticles() {
     const keyword = document.getElementById('search-input').value.trim();