fix(canvas): prevent caching during image export

- Add 'no-cache' option to fetch request for image export
- Ensures fresh image data is always retrieved when exporting canvas

packages/ai-workspace-common/src/hooks/use-export-canvas-as-image.ts

@@ -17,6 +17,7 @@ export const useExportCanvasAsImage = () => {
     try {
       const response = await fetch(imgUrl, {
         mode: 'cors',
+        cache: 'no-cache',
         ...(imgUrl.startsWith(staticPrivateEndpoint) ? { credentials: 'include' } : {}),
       });
       const blob = await response.blob();