style: 优化文章封面图样式以改善显示效果

src/app.css

@@ -1391,20 +1391,18 @@ footer section p:first-child {
 /* Featured Image Styles */
 .post-cover {
 	width: 100%;
-	height: 200px;
+	height: auto;
 	overflow: hidden;
 	border-bottom: none;
-	background-color: var(--border-color); /* 添加一点背景色填补空白区域 */
-	display: flex;
-	align-items: center;
-	justify-content: center;
+	text-align: center;
 }
 
 .post-cover img {
-	width: 100%;
-	height: 100%;
-	object-fit: contain; /* 保证图片显示完整不被裁剪 */
+	max-width: 100%;
+	height: auto;
+	max-height: 260px;
 	display: block;
+	margin: 0 auto;
 	border-radius: 0;
 }