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>

test/berrypod_web/plugs/broken_url_tracker_test.exs

@@ -1,18 +1,25 @@
 defmodule BerrypodWeb.Plugs.BrokenUrlTrackerTest do
   use BerrypodWeb.ConnCase, async: true
 
-  alias Berrypod.Redirects
+  import Berrypod.AccountsFixtures
+
+  alias Berrypod.{Redirects, Settings}
 
   setup do
     Redirects.create_table()
+    # Create admin user so SetupHook allows access
+    user_fixture()
+    # Mark site as live so requests aren't redirected to /coming-soon
+    {:ok, _} = Settings.set_site_live(true)
     :ok
   end
 
   test "records broken URL on 404", %{conn: conn} do
-    # Multi-segment path — not caught by the /:slug catch-all route
-    conn = get(conn, "/zz/nonexistent-path")
-
-    assert conn.status in [404, 500]
+    # Multi-segment path goes through the catch-all route and raises NotFoundError.
+    # The BrokenUrlTracker plug catches this and records it before re-raising.
+    assert_error_sent :not_found, fn ->
+      get(conn, "/zz/nonexistent-path")
+    end
 
     [broken_url] = Redirects.list_broken_urls()
     assert broken_url.path == "/zz/nonexistent-path"
@@ -20,7 +27,11 @@ defmodule BerrypodWeb.Plugs.BrokenUrlTrackerTest do
   end
 
   test "skips static asset paths", %{conn: conn} do
-    get(conn, "/assets/missing-file.js")
+    # Static asset paths should not be recorded as broken URLs.
+    # These raise NotFoundError but the tracker ignores them.
+    assert_error_sent :not_found, fn ->
+      get(conn, "/assets/missing-file.js")
+    end
 
     assert Redirects.list_broken_urls() == []
   end