add nav editors to Site tab with live preview

- Add header and footer nav editors to Site tab with drag-to-reorder,
  add/remove items, and destination picker (pages, collections, external)
- Live preview updates as you edit nav items
- Remove legacy /admin/navigation page and controller (was saving to
  Settings table, now uses nav_items table)
- Update error_html.ex and pages/editor.ex to load nav from nav_items table
- Update link_scanner to read from nav_items table, edit path now /?edit=site
- Add Site.default_header_nav/0 and default_footer_nav/0 for previews/errors
- Remove fallback logic from theme_hook.ex (database is now source of truth)
- Seed default nav items and social links during setup

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

lib/berrypod_web/components/shop_components/layout.ex

@@ -88,18 +88,23 @@ defmodule BerrypodWeb.ShopComponents.Layout do
     base = Map.take(assigns, @layout_keys)
 
     # When site editor is active, use in-memory values for live preview
-    # The site_* assigns are the editor's working copies, while announcement_*
-    # and social_links are the database-loaded values from theme_hook
+    # The site_state assigns is the editor's working copy, while announcement_*,
+    # nav items, and social_links are the database-loaded values from theme_hook
     # Only override when site_editing is true (editor has loaded site state)
-    if assigns[:site_editing] do
-      # Convert raw SocialLink structs to shop format
-      social_links = format_social_links_for_shop(assigns[:site_social_links] || [])
+    if assigns[:site_editing] && assigns[:site_state] do
+      state = assigns[:site_state]
+      # Convert raw structs to shop format
+      social_links = format_social_links_for_shop(state.social_links || [])
+      header_nav = format_nav_items_for_shop(state.header_nav || [])
+      footer_nav = format_nav_items_for_shop(state.footer_nav || [])
 
       base
-      |> Map.put(:announcement_text, assigns[:site_announcement_text])
-      |> Map.put(:announcement_link, assigns[:site_announcement_link])
-      |> Map.put(:announcement_style, assigns[:site_announcement_style])
+      |> Map.put(:announcement_text, state.announcement_text)
+      |> Map.put(:announcement_link, state.announcement_link)
+      |> Map.put(:announcement_style, state.announcement_style)
       |> Map.put(:social_links, social_links)
+      |> Map.put(:header_nav_items, header_nav)
+      |> Map.put(:footer_nav_items, footer_nav)
     else
       base
     end
@@ -122,6 +127,41 @@ defmodule BerrypodWeb.ShopComponents.Layout do
     end)
   end
 
+  # Convert raw NavItem structs to the format expected by shop components
+  # Filters out items with empty labels (incomplete entries still being edited)
+  defp format_nav_items_for_shop(items) do
+    items
+    |> Enum.reject(fn item -> is_nil(item.label) or item.label == "" end)
+    |> Enum.map(fn item ->
+      slug = extract_slug_from_url(item.url)
+
+      base = %{
+        "label" => item.label,
+        "href" => item.url,
+        "slug" => slug
+      }
+
+      # Add active_slugs for Shop nav item to highlight on collection and pdp pages
+      if slug == "collection" do
+        Map.put(base, "active_slugs", ["collection", "pdp"])
+      else
+        base
+      end
+    end)
+  end
+
+  # Extract a slug from a URL for nav item matching
+  defp extract_slug_from_url(url) when is_binary(url) do
+    cond do
+      url == "/" -> "home"
+      String.starts_with?(url, "/collections") -> "collection"
+      String.starts_with?(url, "/products") -> "pdp"
+      true -> url |> String.trim_leading("/") |> String.split("/") |> List.first() || ""
+    end
+  end
+
+  defp extract_slug_from_url(_), do: ""
+
   # Social
   defp platform_display_label("instagram"), do: "Instagram"
   defp platform_display_label("threads"), do: "Threads"