refactor(backtoup): 调整：返回顶部按钮颜色和大小修改

src/components/BackToUp/index.vue

@@ -19,13 +19,13 @@ const { x, y } = useWindowScroll({
   lang="scss">
   .back-to-top {
     position: fixed;
-    bottom: 50px;
+    bottom: 80px;
     right: 24px;
     z-index: 999;
     width: 46px;
     height: 46px;
     border-radius: 50%;
-    background-color: var(--el-bg-color-overlay);
+    background-color: var(--main-color);
     box-shadow: 0 0 10px rgba(0, 0, 0, 0.1);
     cursor: pointer;
     transition: all 0.5s;
@@ -35,8 +35,9 @@ const { x, y } = useWindowScroll({
     align-items: center;
 
     i {
-      font-size: 20px;
-      color: var(--el-text-color-regular)
+      font-size: 28px;
+      font-weight: 900;
+      color: white;
     }
   }
 </style>
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