integrate R module and add url editor ui

Replaces hardcoded paths with R module throughout:
- Shop components: layout nav, cart, product links
- Controllers: cart, checkout, contact, seo, order lookup
- Shop pages: collection, product, search, checkout success, etc.
- Site context: nav item url resolution

Admin URL management:
- Settings page: prefix editor with validation feedback
- Page renderer: url_editor component for page URLs
- CSS for url editor styling

Test updates for cache isolation

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

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

@@ -7,6 +7,7 @@ defmodule BerrypodWeb.Shop.Pages.Contact do
   import Phoenix.LiveView, only: [push_navigate: 2, put_flash: 3]
 
   alias Berrypod.{ContactNotifier, Orders}
+  alias BerrypodWeb.R
   alias Berrypod.Orders.OrderNotifier
   alias Berrypod.Pages
   alias BerrypodWeb.OrderLookupController
@@ -21,7 +22,7 @@ defmodule BerrypodWeb.Shop.Pages.Contact do
         :page_description,
         "Get in touch with us for any questions or help with your order."
       )
-      |> assign(:og_url, BerrypodWeb.Endpoint.url() <> "/contact")
+      |> assign(:og_url, R.url(R.contact()))
       |> assign(:tracking_state, :idle)
       |> assign(:page, page)
 
@@ -54,7 +55,7 @@ defmodule BerrypodWeb.Shop.Pages.Contact do
         {:noreply,
          socket
          |> put_flash(:info, "Message sent! We'll get back to you soon.")
-         |> push_navigate(to: "/contact")}
+         |> push_navigate(to: R.contact())}
 
       {:error, :invalid_params} ->
         {:noreply, put_flash(socket, :error, "Please fill in all required fields.")}