[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

priv/repo/migrations/20240529000015_modify_upload_date_index.exs

@@ -0,0 +1,8 @@
+defmodule Pinchflat.Repo.Migrations.ModifyUploadDateIndex do
+  use Ecto.Migration
+
+  def change do
+    drop index("media_items", [:upload_date])
+    create index("media_items", [:uploaded_at])
+  end
+end