Show recently viewed report pages in dropdown from navbar

We now have this for queries/lists/templates viewed, so maybe it would be useful to have the equivalent for reports?

*Implementation details: Make it a close analog to the results navbar item, just using the summary icon instead.*

*Update: Now that the results navbar dropdown has been expanded with a recent queries header, we could perhaps add another header/separator in this dropdown for recent reports?*

*Post update: Now that the header has been renamed to Recent activity and intent (whether it's a query, template, list, search, etc.) has been added, we could just mix reports in there as well?*

*Post post update: We might want to persist this on mine changes (i.e., save it somewhere else in app-db so it won't get cleared, and is instead restored when you switch back to the mine).*

Start by locating the results navbar item and the existing recent activity dropdown, then trace how viewed queries, lists, and templates are recorded. Decide how reports should appear alongside those entries, including whether activity must persist across mine changes in app-db; done means reports appear in the navbar dropdown and restore correctly when switching back.

Written by the indexing model from the issue text.