feat(editor): 添加预加载动画和编辑器功能优化

- 新增预加载动画组件及样式
- 优化编辑器图片和视频上传处理逻辑
- 修复编辑器内容转换和格式处理问题
- 添加上传进度显示功能
- 改进编辑器工具栏图标和布局

css/public.less

@@ -2273,3 +2273,46 @@ td {
         transform: rotate(360deg);
     }
 }
+
+#pre-loader {
+    height: 70vh;
+    display: flex;
+    justify-content: center;
+    align-items: center;
+
+    .three-bounce {
+        > div {
+            display: inline-block;
+            width: 18px;
+            height: 18px;
+            border-radius: 100%;
+            top: 50%;
+            margin-top: -9px;
+            background: #aeadba;
+            animation: bouncedelay 1.4s infinite ease-in-out;
+            animation-fill-mode: both;
+        }
+
+        .one {
+            animation-delay: -0.32s;
+        }
+
+        .two {
+            animation-delay: -0.16s;
+        }
+    }
+}
+
+@keyframes bouncedelay {
+    0%,
+    100%,
+    80% {
+        transform: scale(0);
+        -webkit-transform: scale(0);
+    }
+
+    40% {
+        transform: scale(1);
+        -webkit-transform: scale(1);
+    }
+}