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/components/shop_components.ex

@@ -9,6 +9,7 @@ defmodule BerrypodWeb.ShopComponents do
   - `Cart` — cart drawer, cart items, order summary
   - `Product` — product cards, gallery, variant selector, hero sections
   - `Content` — rich text, responsive images, contact form, reviews
+  - `ThemeEditor` — shared theme editor components for admin and on-site editing
   """
 
   defmacro __using__(_opts \\ []) do
@@ -18,6 +19,7 @@ defmodule BerrypodWeb.ShopComponents do
       import BerrypodWeb.ShopComponents.Content
       import BerrypodWeb.ShopComponents.Layout
       import BerrypodWeb.ShopComponents.Product
+      import BerrypodWeb.ShopComponents.ThemeEditor
     end
   end
 end