Add a report button to activities view

This was a request from another user that frequently helps staff with reporting questionable posts. Rather than just having the report button in the feed, they would like to have the button within the actual activity posts themselves.

Start by locating the activities view and the existing report button in the feed. Trace how reporting is triggered there, then add equivalent access within each activity post and verify that users can report questionable posts from that view.

Written by the indexing model from the issue text.