add abandoned cart recovery

When a Stripe checkout session expires without payment, if the customer
entered their email, we record an AbandonedCart and schedule a single
plain-text recovery email (1h delay via Oban).

Privacy design:
- feature is off by default; shop owner opts in via admin settings
- only contacts customers who entered their email at Stripe checkout
- single email, never more (emailed_at timestamp gate)
- suppression list blocks repeat contact; one-click unsubscribe via
  signed token (/unsubscribe/:token)
- records pruned after 30 days (nightly Oban cron)
- no tracking pixels, no redirected links, no HTML

Legal notes:
- custom_text added to Stripe session footer when recovery is on
- UK PECR soft opt-in; EU legitimate interests both satisfied by this design

Files:
- migration: abandoned_carts + email_suppressions tables
- schemas: AbandonedCart, EmailSuppression
- context: Orders.create_abandoned_cart, check_suppression, add_suppression,
  has_recent_paid_order?, get_abandoned_cart_by_session, mark_abandoned_cart_emailed
- workers: AbandonedCartEmailWorker (checkout queue), AbandonedCartPruneWorker (cron)
- notifier: OrderNotifier.deliver_cart_recovery/3
- webhook: extended checkout.session.expired handler
- controller: UnsubscribeController, admin settings toggle
- tests: 28 new tests across context, workers, and controller

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

lib/berrypod_web/controllers/stripe_webhook_controller.ex

@@ -86,19 +86,65 @@ defmodule BerrypodWeb.StripeWebhookController do
 
   defp handle_event(%Stripe.Event{type: "checkout.session.expired", data: %{object: session}}) do
     order_id = session.metadata["order_id"]
+    order = Orders.get_order(order_id)
 
-    case Orders.get_order(order_id) do
-      nil -> :ok
-      order -> Orders.mark_failed(order)
-    end
+    if order, do: Orders.mark_failed(order)
 
     Logger.info("Stripe checkout session expired for order #{order_id}")
+
+    if Berrypod.Settings.abandoned_cart_recovery_enabled?() do
+      maybe_create_abandoned_cart(session, order)
+    end
   end
 
   defp handle_event(%Stripe.Event{type: type}) do
     Logger.debug("Unhandled Stripe event: #{type}")
   end
 
+  defp maybe_create_abandoned_cart(_session, nil), do: :ok
+
+  defp maybe_create_abandoned_cart(session, order) do
+    email = session.customer_details && session.customer_details.email
+
+    cond do
+      is_nil(email) or email == "" ->
+        Logger.debug("Cart recovery: no email captured for session #{session.id}")
+
+      Orders.check_suppression(email) == :suppressed ->
+        Logger.debug("Cart recovery: #{email} is suppressed")
+
+      Orders.has_recent_paid_order?(email) ->
+        Logger.debug("Cart recovery: #{email} has a recent paid order, skipping")
+
+      not is_nil(Orders.get_abandoned_cart_by_session(session.id)) ->
+        Logger.debug("Cart recovery: session #{session.id} already recorded")
+
+      true ->
+        create_cart_and_enqueue(session, order, email)
+    end
+  end
+
+  defp create_cart_and_enqueue(session, order, email) do
+    expired_at = DateTime.utc_now() |> DateTime.truncate(:second)
+
+    attrs = %{
+      customer_email: email,
+      order_id: order.id,
+      stripe_session_id: session.id,
+      cart_total: order.total,
+      expired_at: expired_at
+    }
+
+    case Orders.create_abandoned_cart(attrs) do
+      {:ok, cart} ->
+        Berrypod.Orders.AbandonedCartEmailWorker.enqueue(cart.id)
+        Logger.info("Abandoned cart recorded for #{email}, recovery email scheduled")
+
+      {:error, reason} ->
+        Logger.warning("Failed to create abandoned cart: #{inspect(reason)}")
+    end
+  end
+
   defp update_shipping(order, shipping_details) do
     address = shipping_details.address || %{}