Progress Bar on Proof Generation

[#1]

Since proofs of large/complex files can take awhile (like the one I've had processing for an hour or so), it would be helpful to have a progress bar to estimate how much longer it will take.

[#2]

We've had proofs take 5+ hours to generate! We'd also love a popup notification when the proof is done generating:

• Pop-up notification for the producer when a proof is done generating (rather than the email notification ‚Äì which is only saved in their PHQ profile anyway, so most users don’t have access to set this)

[#3]

I would also like to see a percentage, or some other type of indicator, along with the spinner so I can tell if it's processing or has hung up. I've waited for a long time while the spinner was up, then just refreshed my browser and the proof was created.