feat(assets): 使用 file-saver 库优化文件下载功能

- 引入 file-saver 库替代手动创建下载链接的方式
- 在 asset-transfer.ts 中使用 saveAs 替代 URL.createObjectURL 和手动点击链接
- 在 canvas-export.ts 中使用 saveAs 替代原有的文件下载逻辑
- 更新 package.json 添加 file-saver 依赖
- 更新 bun.lock 文件同步依赖变更

web/src/app/(user)/assets/asset-transfer.ts

@@ -1,3 +1,5 @@
+import { saveAs } from "file-saver";
+
 import { createZip, readZip } from "@/lib/zip";
 import { getMediaBlob, setMediaBlob } from "@/services/file-storage";
 import { getImageBlob, setImageBlob } from "@/services/image-storage";
@@ -36,12 +38,7 @@ export async function exportAssets(assets: Asset[]) {
 
     const data: AssetExportFile = { app: "infinite-canvas", version: 1, exportedAt: new Date().toISOString(), assets, files };
     const zip = await createZip([{ name: "assets.json", data: JSON.stringify(data, null, 2) }, ...zipFiles]);
-    const url = URL.createObjectURL(zip);
-    const link = document.createElement("a");
-    link.href = url;
-    link.download = "我的素材.zip";
-    link.click();
-    URL.revokeObjectURL(url);
+    saveAs(zip, "我的素材.zip");
 }
 
 export async function readAssetPackage(file: File) {