refactor: extract announcement_bar to shared ShopComponents module

Move announcement_bar from ThemeLive.PreviewPages to a new shared
SimpleshopThemeWeb.ShopComponents module. This establishes the pattern
for Phase 9 storefront integration where components need to work in
both the admin theme preview and public storefront pages.

Changes:
- Create lib/simpleshop_theme_web/components/shop_components.ex
- Add optional message attribute (defaults to "Free delivery over £40")
- Import ShopComponents in html_helpers for global availability
- Import ShopComponents in PreviewPages for embedded template access
- Update all 7 preview templates to use short-form <.announcement_bar>
- Remove original announcement_bar/1 from PreviewPages (now unused)

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

lib/simpleshop_theme_web/live/theme_live/preview_pages.ex

@@ -1,5 +1,6 @@
 defmodule SimpleshopThemeWeb.ThemeLive.PreviewPages do
   use Phoenix.Component
+  import SimpleshopThemeWeb.ShopComponents
 
   embed_templates "preview_pages/*"
 
@@ -14,22 +15,6 @@ defmodule SimpleshopThemeWeb.ThemeLive.PreviewPages do
     """
   end
 
-  @doc """
-  Renders the announcement bar.
-  """
-  attr :theme_settings, :map, required: true
-
-  def announcement_bar(assigns) do
-    ~H"""
-    <div
-      class="announcement-bar"
-      style="background-color: hsl(var(--t-accent-h) var(--t-accent-s) var(--t-accent-l)); color: var(--t-text-inverse); text-align: center; padding: 0.5rem 1rem; font-size: var(--t-text-small);"
-    >
-      <p style="margin: 0;">Free delivery on orders over £40</p>
-    </div>
-    """
-  end
-
   @doc """
   Renders the shop header with logo based on logo_mode setting.
   """

lib/simpleshop_theme_web/live/theme_live/preview_pages/about.html.heex

@@ -4,7 +4,7 @@
 
   <!-- Announcement Bar -->
   <%= if @theme_settings.announcement_bar do %>
-    <SimpleshopThemeWeb.ThemeLive.PreviewPages.announcement_bar theme_settings={@theme_settings} />
+    <.announcement_bar theme_settings={@theme_settings} />
   <% end %>
 
   <!-- Header -->

lib/simpleshop_theme_web/live/theme_live/preview_pages/cart.html.heex

@@ -4,7 +4,7 @@
 
   <!-- Announcement Bar -->
   <%= if @theme_settings.announcement_bar do %>
-    <SimpleshopThemeWeb.ThemeLive.PreviewPages.announcement_bar theme_settings={@theme_settings} />
+    <.announcement_bar theme_settings={@theme_settings} />
   <% end %>
 
   <!-- Header -->

lib/simpleshop_theme_web/live/theme_live/preview_pages/collection.html.heex

@@ -4,7 +4,7 @@
 
   <!-- Announcement Bar -->
   <%= if @theme_settings.announcement_bar do %>
-    <SimpleshopThemeWeb.ThemeLive.PreviewPages.announcement_bar theme_settings={@theme_settings} />
+    <.announcement_bar theme_settings={@theme_settings} />
   <% end %>
 
   <!-- Header -->

lib/simpleshop_theme_web/live/theme_live/preview_pages/contact.html.heex

@@ -4,7 +4,7 @@
 
   <!-- Announcement Bar -->
   <%= if @theme_settings.announcement_bar do %>
-    <SimpleshopThemeWeb.ThemeLive.PreviewPages.announcement_bar theme_settings={@theme_settings} />
+    <.announcement_bar theme_settings={@theme_settings} />
   <% end %>
 
   <!-- Header -->

lib/simpleshop_theme_web/live/theme_live/preview_pages/error.html.heex

@@ -4,7 +4,7 @@
 
   <!-- Announcement Bar -->
   <%= if @theme_settings.announcement_bar do %>
-    <SimpleshopThemeWeb.ThemeLive.PreviewPages.announcement_bar theme_settings={@theme_settings} />
+    <.announcement_bar theme_settings={@theme_settings} />
   <% end %>
 
   <!-- Header -->

lib/simpleshop_theme_web/live/theme_live/preview_pages/home.html.heex

@@ -4,7 +4,7 @@
 
   <!-- Announcement Bar -->
   <%= if @theme_settings.announcement_bar do %>
-    <SimpleshopThemeWeb.ThemeLive.PreviewPages.announcement_bar theme_settings={@theme_settings} />
+    <.announcement_bar theme_settings={@theme_settings} />
   <% end %>
 
   <!-- Header -->

lib/simpleshop_theme_web/live/theme_live/preview_pages/pdp.html.heex

@@ -7,7 +7,7 @@
 
   <!-- Announcement Bar -->
   <%= if @theme_settings.announcement_bar do %>
-    <SimpleshopThemeWeb.ThemeLive.PreviewPages.announcement_bar theme_settings={@theme_settings} />
+    <.announcement_bar theme_settings={@theme_settings} />
   <% end %>
 
   <!-- Header -->