add newsletter and email campaigns

Subscribers with double opt-in confirmation, campaign composer with
draft/scheduled/sent lifecycle, admin dashboard with overview stats,
CSV export, and shop signup form wired into page builder blocks.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

test/support/fixtures/newsletter_fixtures.ex

@@ -0,0 +1,40 @@
+defmodule Berrypod.NewsletterFixtures do
+  @moduledoc """
+  Test helpers for creating newsletter subscribers and campaigns.
+  """
+
+  alias Berrypod.Newsletter
+
+  def unique_email, do: "user#{System.unique_integer([:positive])}@example.com"
+
+  @doc """
+  Creates a confirmed subscriber directly via Repo, bypassing the
+  confirmation email flow.
+  """
+  def confirmed_subscriber_fixture(attrs \\ %{}) do
+    now = DateTime.utc_now() |> DateTime.truncate(:second)
+
+    attrs =
+      Enum.into(attrs, %{
+        email: unique_email(),
+        status: "confirmed",
+        confirmed_at: now,
+        consent_text: "Test signup"
+      })
+
+    %Newsletter.Subscriber{}
+    |> Newsletter.Subscriber.changeset(attrs)
+    |> Berrypod.Repo.insert!()
+  end
+
+  def campaign_fixture(attrs \\ %{}) do
+    attrs =
+      Enum.into(attrs, %{
+        subject: "Test campaign #{System.unique_integer([:positive])}",
+        body: "Hello! Unsubscribe: {{unsubscribe_url}}"
+      })
+
+    {:ok, campaign} = Newsletter.create_campaign(attrs)
+    campaign
+  end
+end