add send test email button to campaign form

Sends the campaign to the admin's own email address as a preview,
with [Test] prefix in subject line. Uses the same HTML template
and formatting as real sends. Does not affect campaign status or
sent counts.

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

lib/berrypod_web/live/admin/newsletter/campaign_form.ex

@@ -74,6 +74,29 @@ defmodule BerrypodWeb.Admin.Newsletter.CampaignForm do
     end
   end
 
+  def handle_event("send_test", _params, socket) do
+    params = current_form_params(socket)
+    to_email = socket.assigns.current_scope.user.email
+
+    if params["subject"] == "" || params["body"] == "" do
+      {:noreply, put_flash(socket, :error, "Fill in subject and body first")}
+    else
+      # Build a temporary campaign struct for the notifier
+      campaign = %Newsletter.Campaign{
+        subject: params["subject"],
+        body: params["body"]
+      }
+
+      case Newsletter.Notifier.deliver_test(campaign, to_email) do
+        {:ok, _} ->
+          {:noreply, put_flash(socket, :info, "Test email sent to #{to_email}")}
+
+        {:error, _} ->
+          {:noreply, put_flash(socket, :error, "Failed to send test email")}
+      end
+    end
+  end
+
   def handle_event("schedule", _params, socket) do
     params = current_form_params(socket)
     scheduled_at = parse_schedule_time(params["scheduled_at"])
@@ -184,6 +207,14 @@ defmodule BerrypodWeb.Admin.Newsletter.CampaignForm do
               Save draft
             </.button>
 
+            <button
+              type="button"
+              phx-click="send_test"
+              class="admin-btn admin-btn-ghost"
+            >
+              <.icon name="hero-envelope" class="size-4" /> Send test
+            </button>
+
             <button
               type="button"
               phx-click="send_now"