Activity log for each return

[dpath]

It would be really helpful if ProConnect had an activity log at the return level.

For firms with multiple preparers and reviewers, we need better visibility into what work has actually been done on each return. Right now, it seems like we have to rely heavily on team members manually updating the status, which can be hard to track and verify.

An activity log could show things like:

* Who opened or worked on the return
* When the return was last updated
* What sections/forms were edited
* Who assigned or reassigned the return
* Whether diagnostics, review, or e-file steps were completed

This would help firms track progress more accurately, especially when several CPAs/preparers are working in the same account. It would also reduce the need to rely only on status updates or external trackers to know what is actually in progress.