Fix Dialyzer opaque type warning in register_user_with_organization

- Create changeset before Multi pipeline for better type inference
- Pass changeset directly to Multi.insert instead of using function form
- Resolves call_without_opaque warning at line 97

lib/towerops/accounts.ex

@@ -94,10 +94,10 @@ defmodule Towerops.Accounts do
 
   """
   def register_user_with_organization(attrs) do
+    user_changeset = User.email_changeset(%User{}, attrs)
+
     Ecto.Multi.new()
-    |> Ecto.Multi.insert(:user, fn _ ->
-      User.email_changeset(%User{}, attrs)
-    end)
+    |> Ecto.Multi.insert(:user, user_changeset)
     |> Ecto.Multi.run(:organization, fn _repo, %{user: user} ->
       org_name = attrs["organization_name"] || "Personal"