拆分图片画布上传工作流

新增图片文件读取模型和上传工作流 hook

把上传目标分发、登录续传、占位卡片和画布建层从主视图抽出

补充上传工作流单测并更新拆分计划和进度记录

src/components/image-editor/useImageCanvasAssetLibrary.ts

@@ -29,6 +29,7 @@ import type {
   EditorAsset,
   EditorAssetFolder,
 } from './ImageCanvasEditorTypes';
+export { readImageFileAsDataUrl } from './ImageCanvasFileModel';
 
 function isEditorAuthError(error: unknown) {
   return (
@@ -37,21 +38,6 @@ function isEditorAuthError(error: unknown) {
   );
 }
 
-export function readImageFileAsDataUrl(file: File) {
-  return new Promise<string>((resolve, reject) => {
-    const reader = new FileReader();
-    reader.onload = () => {
-      if (typeof reader.result === 'string') {
-        resolve(reader.result);
-        return;
-      }
-      reject(new Error('图片读取失败'));
-    };
-    reader.onerror = () => reject(reader.error ?? new Error('图片读取失败'));
-    reader.readAsDataURL(file);
-  });
-}
-
 export function useImageCanvasAssetLibrary({
   assetListRef,
   openEditorLoginModal,