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/controllers/error_html.ex

@@ -149,14 +149,8 @@ defmodule BerrypodWeb.ErrorHTML do
       |> Map.put(:cart_count, 0)
       |> Map.put(:cart_subtotal, "£0.00")
       |> Map.put(:page, page)
-      |> Map.put(
-        :header_nav_items,
-        load_nav("header_nav", &BerrypodWeb.ThemeHook.default_header_nav/0)
-      )
-      |> Map.put(
-        :footer_nav_items,
-        load_nav("footer_nav", &BerrypodWeb.ThemeHook.default_footer_nav/0)
-      )
+      |> Map.put(:header_nav_items, load_nav_items("header"))
+      |> Map.put(:footer_nav_items, load_nav_items("footer"))
 
     # Load block data (e.g. products for featured_products block)
     extra = safe_load(fn -> Pages.load_block_data(page.blocks, assigns) end) || %{}
@@ -223,10 +217,15 @@ defmodule BerrypodWeb.ErrorHTML do
     end
   end
 
-  defp load_nav(key, default_fn) do
-    case safe_load(fn -> Settings.get_setting(key) end) do
-      items when is_list(items) -> items
-      _ -> default_fn.()
+  # Load nav items from database, falling back to defaults if DB fails
+  # (error pages might render when database is unavailable)
+  defp load_nav_items(location) do
+    case safe_load(fn -> Berrypod.Site.nav_items_for_shop(location) end) do
+      items when is_list(items) and items != [] -> items
+      _ -> default_nav_items(location)
     end
   end
+
+  defp default_nav_items("header"), do: Berrypod.Site.default_header_nav()
+  defp default_nav_items("footer"), do: Berrypod.Site.default_footer_nav()
 end

lib/berrypod_web/controllers/navigation_controller.ex

@@ -1,81 +0,0 @@
-defmodule BerrypodWeb.NavigationController do
-  @moduledoc """
-  No-JS fallback for navigation form submission.
-
-  With JS enabled, the LiveView handles everything. Without JS,
-  the form POSTs here and we redirect back to the LiveView page.
-  """
-  use BerrypodWeb, :controller
-
-  alias Berrypod.Settings
-
-  def save(conn, %{"header_nav" => header_json, "footer_nav" => footer_json}) do
-    with {:ok, header_items} <- Jason.decode(header_json),
-         {:ok, footer_items} <- Jason.decode(footer_json) do
-      all_items = header_items ++ footer_items
-      errors = validate_nav_items(all_items)
-
-      if errors == [] do
-        Settings.put_setting("header_nav", header_items, "json")
-        Settings.put_setting("footer_nav", footer_items, "json")
-
-        conn
-        |> put_flash(:info, "Navigation saved")
-        |> redirect(to: ~p"/admin/navigation")
-      else
-        conn
-        |> put_flash(:error, Enum.join(errors, ". "))
-        |> redirect(to: ~p"/admin/navigation")
-      end
-    else
-      {:error, _} ->
-        conn
-        |> put_flash(:error, "Invalid navigation data")
-        |> redirect(to: ~p"/admin/navigation")
-    end
-  end
-
-  defp validate_nav_items(items) do
-    items
-    |> Enum.flat_map(fn item ->
-      cond do
-        item["label"] == "" || item["label"] == nil ->
-          ["All links need a label"]
-
-        item["href"] == "" || item["href"] == nil ->
-          ["\"#{item["label"]}\" needs a destination"]
-
-        item["external"] == true || is_external_url?(item["href"]) ->
-          if valid_url?(item["href"]) do
-            []
-          else
-            ["\"#{item["label"]}\" has an invalid URL"]
-          end
-
-        true ->
-          []
-      end
-    end)
-    |> Enum.uniq()
-  end
-
-  defp valid_url?(url) when is_binary(url) do
-    case URI.parse(url) do
-      %URI{scheme: scheme, host: host}
-      when scheme in ["http", "https"] and is_binary(host) and host != "" ->
-        true
-
-      _ ->
-        false
-    end
-  end
-
-  defp valid_url?(_), do: false
-
-  defp is_external_url?(nil), do: false
-  defp is_external_url?(""), do: false
-
-  defp is_external_url?(href) do
-    String.starts_with?(href, "http://") || String.starts_with?(href, "https://")
-  end
-end