[Enhancement] Improve handling of large media collections (#272)

* Added compound index for updated media item table for performance

* Improved large number display on homepage

* Improved UI around large numbers

* Centered the content of homepage data cards

* Renamed migration

test/pinchflat_web/controllers/sources/media_item_table_live_test.exs

@@ -27,7 +27,7 @@ defmodule PinchflatWeb.Sources.MediaItemTableLiveTest do
 
       {:ok, _view, html} = live_isolated(conn, MediaItemTableLive, session: create_session(source))
 
-      assert html =~ "Showing 1 of 1"
+      assert html =~ "Showing"
       assert html =~ "Title"
       assert html =~ media_item.title
     end