[Enhancement] Record and display errors related to downloading (#610)

* Added last_error to media item table

* Error messages are now persisted to the last_error field

* Minor layout updates

* Added help tooltip to source content view

* Added error information to homepage tables

* Remove unneeded index

* Added docs to tooltip component

priv/repo/migrations/20250210201413_add_last_error_to_media_item.exs

@@ -0,0 +1,9 @@
+defmodule Pinchflat.Repo.Migrations.AddLastErrorToMediaItem do
+  use Ecto.Migration
+
+  def change do
+    alter table(:media_items) do
+      add :last_error, :string
+    end
+  end
+end