consolidate shop pages into unified LiveView for editor state persistence

Replace individual shop LiveViews with a single Shop.Page that dispatches
to page modules based on live_action. This enables patch navigation between
pages, preserving socket state (including editor state) across transitions.

Changes:
- Add Shop.Page unified LiveView with handle_params dispatch
- Extract page logic into Shop.Pages.* modules (Home, Product, Collection, etc.)
- Update router to use Shop.Page with live_action for all shop routes
- Change navigate= to patch= in shop component links
- Add maybe_sync_editing_blocks to reload editor state when page changes
- Track editor_page_slug to detect cross-page navigation while editing
- Fix picture element height when hover image disabled
- Extract ThemeEditor components for shared use

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

lib/berrypod_web/live/shop/coming_soon.ex

@@ -6,6 +6,11 @@ defmodule BerrypodWeb.Shop.ComingSoon do
     {:ok, assign(socket, :page_title, "Coming soon")}
   end
 
+  @impl true
+  def handle_params(_params, _uri, socket) do
+    {:noreply, socket}
+  end
+
   @impl true
   def render(assigns) do
     ~H"""