[Enhancement] Add media count to sources page (#251)

* [WIP] Got query kinda working, now to refactor other queries

* Refactored all query methods to use dynamic snippets

* Refactored tab layout to grab tabs by name

* Removed standalone show buttons from in-app tables

* Removed unneeded comment

lib/pinchflat_web/controllers/pages/page_controller.ex

@@ -26,7 +26,7 @@ defmodule PinchflatWeb.Pages.PageController do
       source_count: Repo.aggregate(Source, :count, :id),
       media_item_count:
         MediaQuery.new()
-        |> MediaQuery.with_media_downloaded_at()
+        |> where(^MediaQuery.downloaded())
         |> Repo.aggregate(:count, :id)
     )
   end