Block file uploads when credits are insufficient

When I tried to upload files with no credits remaining, the upload flow appeared to start normally — the UI showed the files as uploading. But since there weren't enough credits to process them, the uploads never actually completed.

When I went to check my Library, the files weren't there. I had to top up my credits and then manually click "Try Again" on each file individually.

It would be much better if the upload flow checked my credit balance before starting. If I don't have enough credits, I'd want to be shown a clear message upfront letting me know and prompting me to top up — rather than letting the upload appear to proceed and then failing silently.