refactor: apply review changes to joinrequest

priv/repo/migrations/20260309141437_add_join_requests.exs

@@ -9,6 +9,7 @@ defmodule Mv.Repo.Migrations.AddJoinRequests do
   use Ecto.Migration
 
   def up do
+    # uuid_generate_v7() is provided by initialize_extensions migration (custom function)
     create table(:join_requests, primary_key: false) do
       add :id, :uuid, null: false, default: fragment("uuid_generate_v7()"), primary_key: true