Fix image generated not available after some time

[mingming-ma]

The image generated will be not available due to URL lifetime ( #493 )

Need to figure out how to store so user can back check them later.

DALL-E API Image URL lifetime

[rjwignar]

I ran into this issue while working on a class project.
We ended up using Cloudinary's free tier to store DALL-E-generated images, but
a better solution for ChatCraft might be to use a local object storage instance.

@humphd we're already using R2 to store local chats, would it be a good idea to store these images in R2 as well?

[humphd]

For shared chats, yes. For local ones, they will be in db.

[mingming-ma]

so a possible fix maybe, don't know fetch again in the response is a good idea

    const imageDataUrls = await Promise.all(response.data.map(async (img: any) => {
      const imageResponse = await fetch(img.url);
      const imageBlob = await imageResponse.blob();
      const imageDataUrl = URL.createObjectURL(imageBlob);
      return imageDataUrl;
    }));