Per-file reviewer comments

[bloodearnest]

Adds a basic text box for users to enter comments for each file.

There is some complexity in whether comments are required:

• If ACRO passed, rejecting the output requires a comment.
• If ACRO failed, approving the output requires a comment.
• If ACRO punted (custom), a comment is required either way.

For now, comments are just logged in the audit log.