Add scheduler selection for good Flux experience (Flux currently is working with this app via forge-api)

[fm3at]

I noticed that your application can work with Flux (flux-bnb4 model in all-in-one format) through the api stable-diffusion-webui-forge. but to correctly display the image, we need to choose an appropriate scheduler. could you add the ability to select a scheduler? flux produces a normal image with simple and beta schedulers. without scheduler selection, on various samplers Flux produces a blurry or completely black image because an automatic scheduler is selected by default.