fix page settings section and blocks not showing in editor

Two bugs fixed:

1. Page Settings section wasn't appearing for system pages because
   Defaults.for_slug didn't return all required fields (type,
   meta_description, published, etc). Also changed page_renderer
   to use bracket notation for safer field access.

2. Blocks weren't loading when navigating directly to ?edit=page
   because the PageEditorHook's handle_params ran before Shop.Page
   assigned @page. Added pending page mode mechanism: hook sets a
   flag when edit mode is requested but @page is nil, then Shop.Page
   calls maybe_enter_pending_page_mode after @page is assigned.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

lib/berrypod_web/page_editor_hook.ex

@@ -81,6 +81,21 @@ defmodule BerrypodWeb.PageEditorHook do
     {:cont, socket}
   end
 
+  @doc """
+  Called by Shop.Page after @page is assigned. If edit mode was requested via
+  URL but couldn't be entered because @page wasn't available yet, enters it now.
+  """
+  def maybe_enter_pending_page_mode(socket) do
+    if socket.assigns[:editor_pending_page_mode] && socket.assigns[:page] &&
+         !socket.assigns.editing do
+      socket
+      |> assign(:editor_pending_page_mode, false)
+      |> enter_edit_mode()
+    else
+      socket
+    end
+  end
+
   # ── handle_params: track current path and restore editor state ────
 
   defp handle_editor_params(params, uri, socket) do
@@ -164,7 +179,8 @@ defmodule BerrypodWeb.PageEditorHook do
       if socket.assigns[:page] do
         enter_edit_mode(socket)
       else
-        socket
+        # Page not yet loaded - mark that we need to enter edit mode when it is
+        assign(socket, :editor_pending_page_mode, true)
       end
     end
   end