wire order pages and theme preview to page renderer, remove old templates

All 14 pages now render through PageRenderer. Theme editor preview
unified from 10 preview_page clauses to one function + page-context
helpers. PageTemplates module and 10 .heex template files deleted.

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

lib/berrypod_web/page_renderer.ex

@@ -856,7 +856,6 @@ defmodule BerrypodWeb.PageRenderer do
   defp collection_path(slug, "featured"), do: ~p"/collections/#{slug}"
   defp collection_path(slug, sort), do: ~p"/collections/#{slug}?sort=#{sort}"
 
-  # Reuse from PageTemplates
   def format_order_status("unfulfilled"), do: "Being prepared"
   def format_order_status("submitted"), do: "Sent to printer"
   def format_order_status("processing"), do: "In production"