fix: 移除不正确的背景图类型（原始大小）

src/hooks/useSlideBackgroundStyle.ts

@@ -27,7 +27,7 @@ export default (background: Ref<SlideBackground | undefined>) => {
         return {
           backgroundImage: `url(${image}`,
           backgroundRepeat: 'repeat',
-          backgroundSize: 'initial',
+          backgroundSize: 'contain',
         }
       }
       return {

src/types/slides.ts

@@ -178,7 +178,7 @@ export interface SlideBackground {
   type: 'solid' | 'image' | 'gradient';
   color?: string;
   image?: string;
-  imageSize?: 'cover' | 'contain' | 'repeat' | 'initial';
+  imageSize?: 'cover' | 'contain' | 'repeat';
   gradientType?: 'linear' | 'radial';
   gradientColor?: [string, string];
   gradientRotate?: number;

src/views/Editor/Toolbar/SlideDesignPanel.vue

@@ -25,11 +25,10 @@
 
       <Select 
         style="flex: 10;" 
-        :value="background.size || 'cover'" 
+        :value="background.imageSize || 'cover'" 
         @change="value => updateBackground({ imageSize: value })"
         v-else-if="background.type === 'image'"
       >
-        <SelectOption value="initial">原始大小</SelectOption>
         <SelectOption value="contain">缩放</SelectOption>
         <SelectOption value="repeat">拼贴</SelectOption>
         <SelectOption value="cover">缩放铺满</SelectOption>