feat: image gen - comfy option - save workflow exif

[qrkourier]

Is your feature request related to a problem? Please describe.
The images are saved, but devoid of exif data.

Describe the solution you'd like
It's a feature of comfy to save the inputs and workflow in the output image exif data. It would be helpful to have the option to enable this because, while more privacy conscious to omit it, it is very useful for iterating on an image by loading it in comfy. Many users will appreciate this option, but it should not be enabled by default.

Describe alternatives you've considered
I considered trying to reproduce the image from scratch in comfy, but open-webui is opaque about the input parameters so it's unclear where to start.

Additional context
The default prompt (comfy workflow) is inline in https://github.com/open-webui/open-webui/blob/v0.1.123/backend/apps/images/utils/comfyui.py#L18

The SaveImage class in comfy always saves exif data, so it may actually be a comfy bug that the image returned by the API is missing those metadata: https://github.com/comfyanonymous/ComfyUI/blob/daa92a8ff4d3e75a3b17bb1a6b6c508b27264ff5/nodes.py#L1380