add SEO enhancements: OG images, meta robots, FAQ block, image sitemap

- Per-page SEO controls: meta robots directives, focus keyword, OG image
- Site-wide default OG image in admin settings
- FAQ block type with FAQPage JSON-LD schema
- Enhanced Organization JSON-LD with business info, contact, address
- Image sitemap with product images
- SEO preview panel with Google/social card mockups
- SEO checklist with real-time scoring
- Business info section in site editor
- GSC integration scaffolding (OAuth, client, cache)

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

lib/berrypod_web/live/shop/pages/cart.ex

@@ -14,10 +14,21 @@ defmodule BerrypodWeb.Shop.Pages.Cart do
       socket
       |> assign(:page_title, "Cart")
       |> assign(:page, page)
+      |> maybe_assign_meta_robots(page)
 
     {:noreply, socket}
   end
 
+  defp maybe_assign_meta_robots(socket, page) do
+    meta_robots = page && page[:meta_robots]
+
+    if meta_robots && meta_robots != "index, follow" do
+      assign(socket, :meta_robots, meta_robots)
+    else
+      socket
+    end
+  end
+
   def handle_params(_params, _uri, socket) do
     {:noreply, socket}
   end