refactor: translate comments and improve code readability

Update comments from Chinese to English for better international collaboration
Standardize comment style across HTML, CSS and JavaScript files
Remove unnecessary comments about global variables

css/style.css

@@ -13,7 +13,7 @@ body {
     color: #ffffff;
 }
 
-/* 主容器 */
+/* Main container */
 .youtube-container {
     display: flex;
     flex-direction: column;
@@ -21,7 +21,7 @@ body {
     overflow: hidden;
 }
 
-/* 顶栏样式 */
+/* Header styles */
 .header {
     display: flex;
     align-items: center;
@@ -157,14 +157,14 @@ body {
     font-size: 20px;
 }
 
-/* 主内容区 */
+/* Main content area */
 .main-content {
     display: flex;
     flex: 1;
     overflow: hidden;
 }
 
-/* 侧边栏样式 */
+/* Sidebar styles */
 .sidebar {
     width: 240px;
     background-color: #000000;
@@ -287,7 +287,7 @@ body {
     border-top: 1px solid #303030;
 }
 
-/* 视频内容区 */
+/* Video content area */
 .video-content {
     flex: 1;
     overflow-y: auto;
@@ -295,7 +295,7 @@ body {
     background-color: #121212;
 }
 
-/* 板块按钮 */
+/* Category buttons */
 .category-buttons {
     display: flex;
     gap: 12px;
@@ -325,7 +325,7 @@ body {
     border-color: #ffffff;
 }
 
-/* 视频网格 */
+/* Video grid */
 .video-grid {
     display: grid;
     grid-template-columns: repeat(auto-fill, minmax(550px, 1fr));
@@ -333,7 +333,7 @@ body {
     margin-bottom: 48px;
 }
 
-/* 视频卡片 */
+/* Video card */
 .video-card {
     background-color: #202020;
     border-radius: 12px;
@@ -512,7 +512,7 @@ body {
     gap: 20px;
 }
 
-/* Shorts 卡片 */
+/* Shorts card */
 .shorts-card {
     position: relative;
     width: 100%;
@@ -573,7 +573,7 @@ body {
     margin-right: 4px;
 }
 
-/* 搜索结果弹窗 */
+/* Search results popup */
 .search-results {
     position: fixed;
     top: 56px;
@@ -659,7 +659,7 @@ body {
     color: #ffffff;
 }
 
-/* 响应式设计 */
+/* Responsive design */
 @media (max-width: 1600px) {
     .video-grid {
         grid-template-columns: repeat(auto-fill, minmax(500px, 1fr));
@@ -727,7 +727,7 @@ body {
     }
 }
 
-/* 滚动条样式 - Webkit浏览器 */
+/* Scrollbar styles - Webkit browsers */
 ::-webkit-scrollbar {
     width: 12px;
     height: 12px;