Changed action_date to created_at in activity report

[snipe]

The value of action_date is not always present, since it's largely used to back-date or forward-date actions without compromising the date the actual thing happened. This just fixes the sorting on the activity report.

[what-the-diff]

PR Summary

• Introduction of 'action_date' field
  A new piece of information, labelled 'action_date', has been added to our reporting system, enhancing the details available in the report. Mainly, now you can see exactly when certain actions took place.

• Field Renaming for Better Comprehension
  To improve the clarity of our reports, we've changed the name of 'action_date' to 'created_at' in the report view. This makes it more intuitive as 'created_at' clearly points out the time when an activity was initiated.