migrate accent colours from HSL to oklch, inject theme into admin

Phase 1: Replace hex_to_hsl with hex_to_oklch in CSSGenerator, output
--t-accent-l/c/h instead of --t-accent-h/s/l. All 46 HSL accent
references across theme-semantic.css, theme-layer2-attributes.css, and
shop/components.css replaced with oklch/color-mix equivalents. Dead
style*= attribute selectors for button variants replaced with proper
class-based selectors. Added color-scheme: light/dark to mood output.

Phase 2: Add LoadTheme plug to admin pipeline, extend AdminLayoutHook
with theme_settings and generated_css assigns, add font preloads and
generated CSS injection to admin_root.html.heex. No visual changes to
admin yet — .themed wrapper added in next phase.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

lib/berrypod_web/admin_layout_hook.ex

@@ -1,21 +1,40 @@
 defmodule BerrypodWeb.AdminLayoutHook do
   @moduledoc """
-  LiveView on_mount hook that assigns the current path for admin sidebar navigation.
+  LiveView on_mount hook that assigns the current path for admin sidebar navigation
+  and loads theme settings for the admin layout.
   """
   import Phoenix.Component
 
+  alias Berrypod.Settings
+  alias Berrypod.Theme.{CSSCache, CSSGenerator}
+
   def on_mount(:assign_current_path, _params, _session, socket) do
+    theme_settings = Settings.get_theme_settings()
+
+    generated_css =
+      case CSSCache.get() do
+        {:ok, css} ->
+          css
+
+        :miss ->
+          css = CSSGenerator.generate(theme_settings, &BerrypodWeb.Endpoint.static_path/1)
+          CSSCache.put(css)
+          css
+      end
+
     socket =
       socket
       |> assign(:current_path, "")
-      |> assign(:site_live, Berrypod.Settings.site_live?())
+      |> assign(:site_live, Settings.site_live?())
+      |> assign(:theme_settings, theme_settings)
+      |> assign(:generated_css, generated_css)
       |> Phoenix.LiveView.attach_hook(:set_current_path, :handle_params, fn _params,
                                                                             uri,
                                                                             socket ->
         {:cont,
          socket
          |> assign(:current_path, URI.parse(uri).path)
-         |> assign(:site_live, Berrypod.Settings.site_live?())}
+         |> assign(:site_live, Settings.site_live?())}
       end)
 
     {:cont, socket}

lib/berrypod_web/components/layouts/admin_root.html.heex

@@ -7,12 +7,23 @@
     <.live_title default="Admin" suffix=" · Berrypod">
       {assigns[:page_title]}
     </.live_title>
+    <!-- Preload critical fonts for the current typography preset -->
+    <%= for preload <- Berrypod.Theme.Fonts.preload_links(
+          @theme_settings.typography,
+          &BerrypodWeb.Endpoint.static_path/1
+        ) do %>
+      <link rel="preload" href={preload.href} as="font" type="font/woff2" crossorigin />
+    <% end %>
     <!-- Pre-declare layer order so shop reset < Tailwind base regardless of load order -->
     <style>
       @layer properties, reset, primitives, tokens, theme, base, components, layout, utilities, overrides;
     </style>
     <link phx-track-static rel="stylesheet" href={~p"/assets/css/admin.css"} />
     <link phx-track-static rel="stylesheet" href={~p"/assets/css/shop.css"} />
+    <!-- Generated theme CSS with @font-face declarations -->
+    <style id="theme-css">
+      <%= Phoenix.HTML.raw(@generated_css) %>
+    </style>
     <script defer phx-track-static src={~p"/assets/js/app.js"}>
     </script>
     <script>

lib/berrypod_web/router.ex

@@ -40,6 +40,7 @@ defmodule BerrypodWeb.Router do
 
   pipeline :admin do
     plug :put_root_layout, html: {BerrypodWeb.Layouts, :admin_root}
+    plug BerrypodWeb.Plugs.LoadTheme
   end
 
   # Public storefront (root level)