fix email settings: hidden attr for no-CSS, block-level card labels

Non-selected adapter configs now get HTML hidden attribute so only the
active config shows without CSS. Provider card labels use div instead
of span for natural block stacking in text-only rendering.

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

test/berrypod_web/live/admin/email_settings_test.exs

@@ -251,6 +251,22 @@ defmodule BerrypodWeb.Admin.EmailSettingsTest do
       assert html =~ "Email provider"
       assert html =~ "sr-only"
     end
+
+    test "only selected adapter config is visible (hidden attribute)", %{conn: conn} do
+      {:ok, view, _html} = live(conn, ~p"/admin/settings/email")
+
+      # Select SMTP
+      view
+      |> form("form[phx-change=\"form_change\"]", %{email: %{adapter: "smtp"}})
+      |> render_change()
+
+      # SMTP should not be hidden
+      refute has_element?(view, ~s([data-adapter="smtp"][hidden]))
+      # Others should be hidden
+      assert has_element?(view, ~s([data-adapter="brevo"][hidden]))
+      assert has_element?(view, ~s([data-adapter="sendgrid"][hidden]))
+      assert has_element?(view, ~s([data-adapter="postal"][hidden]))
+    end
   end
 
   describe "unauthenticated" do