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.css

@@ -1891,3 +1891,38 @@ td {
     transform: rotate(360deg);
   }
 }
+#pre-loader {
+  height: 70vh;
+  display: flex;
+  justify-content: center;
+  align-items: center;
+}
+#pre-loader .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;
+}
+#pre-loader .three-bounce .one {
+  animation-delay: -0.32s;
+}
+#pre-loader .three-bounce .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);
+  }
+}