Add missing FK index on record_set_items.record_id

priv/repo/migrations/20260305142941_add_record_id_index_to_record_set_items.exs

@@ -0,0 +1,8 @@
+defmodule MusicLibrary.Repo.Migrations.AddRecordIdIndexToRecordSetItems do
+  use Ecto.Migration
+
+  def change do
+    # Speeds up queries filtering by record_id alone (e.g., record deletion cascades, cross-set lookups)
+    create index(:record_set_items, [:record_id])
+  end
+end