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/live/shop/page.ex

@@ -237,6 +237,9 @@ defmodule BerrypodWeb.Shop.Page do
     # Must run after handle_params since Content pages set @page there.
     socket = maybe_sync_editing_blocks(socket)
 
+    # If edit mode was requested via URL but @page wasn't available yet, enter it now
+    socket = BerrypodWeb.PageEditorHook.maybe_enter_pending_page_mode(socket)
+
     {:noreply, socket}
   end