feat: 更名 EasyNavi，优化侧边栏

frontend/src/App.jsx

@@ -130,7 +130,7 @@ function App() {
         <div className="sidebar-header">
           <div className="logo">
             <div className="logo-icon"><Icon name="bookmark"/></div>
-            <span className="logo-text">导航收藏夹</span>
+            <span className="logo-text">EasyNavi</span>
           </div>
         </div>
 
@@ -158,9 +158,7 @@ function App() {
         </div>
 
         <div className="sidebar-footer">
-          <button className="add-btn" onClick={() => openModal('category')} style={{ marginBottom: '8px' }}>
-            <Icon name="folder" size={14}/><span>管理分类</span>
-          </button>
+          
           <button className="add-btn" onClick={() => openModal('website')}>
             <Icon name="plus" size={14}/><span>添加网站</span>
           </button>