feat(ui): 优化项目描述折叠交互与样式

- 调整项目描述最大高度从100px到80px
- 更新折叠遮罩渐变效果适配日夜主题
- 重构切换按钮样式为内联文本链接形式
- 修改展开收起逻辑使用innerHTML动态更新内容
- 添加箭头图标指示当前折叠状态
- 移除冗余CSS类定义提升代码整洁度

css/about.css

@@ -1476,23 +1476,33 @@ a:not(.nav-logo):not(.nav-links a):not(.social-link):not(.btn):not(.footer-info
     margin-bottom: 1.5rem;
     line-height: 1.6;
     font-weight: 500;
-}
-
-/* 项目描述折叠样式 */
-.project-description.collapsible {
     position: relative;
-    max-height: 100px;
-    overflow: hidden;
 }
 
-.project-description.collapsible::after {
+.project-description.collapsible {
+    max-height: 80px;
+    overflow: hidden;
+    position: relative;
+}
+
+.theme-day .project-description.collapsible::after {
     content: "";
     position: absolute;
     bottom: 0;
     left: 0;
     right: 0;
-    height: 40px;
-    background: linear-gradient(to bottom, transparent, rgba(255, 255, 255, var(--glass-alpha)));
+    height: 30px;
+    background: linear-gradient(to bottom, transparent, rgba(248, 249, 250, 0.8));
+}
+
+.theme-night .project-description.collapsible::after {
+    content: "";
+    position: absolute;
+    bottom: 0;
+    left: 0;
+    right: 0;
+    height: 30px;
+    background: linear-gradient(to bottom, transparent, rgba(30, 30, 30, 0.8));
 }
 
 .project-description.expanded {
@@ -1503,28 +1513,28 @@ a:not(.nav-logo):not(.nav-links a):not(.social-link):not(.btn):not(.footer-info
     display: none;
 }
 
-.project-description.collapsible {
-    position: relative;
-}
-
 .toggle-description {
-    background: rgba(255, 255, 255, 0.1);
     color: var(--text-strong);
+    background: none;
     border: none;
-    padding: 0.5rem 1rem;
-    border-radius: 20px;
     cursor: pointer;
     font-size: 0.9rem;
-    margin-top: 1rem;
-    transition: all 0.3s ease;
+    margin-left: 5px;
+    vertical-align: baseline;
+    text-decoration: underline;
+    padding: 0;
+    display: inline-flex;
+    align-items: center;
+    gap: 3px;
 }
 
 .toggle-description:hover {
-    background: rgba(255, 255, 255, 0.2);
+    opacity: 0.8;
 }
 
-.project-description.collapsible + .toggle-description {
-    display: inline-block;
+.arrow {
+    font-size: 0.8em;
+    margin-left: 2px;
 }
 
 .project-stats {