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>

test/berrypod_web/live/shop/search_integration_test.exs

@@ -86,13 +86,13 @@ defmodule BerrypodWeb.Shop.SearchIntegrationTest do
   end
 
   describe "search results rendering" do
-    test "result links use navigate for LiveView navigation", %{conn: conn, mountain: mountain} do
+    test "result links use patch for LiveView navigation", %{conn: conn, mountain: mountain} do
       {:ok, view, _html} = live(conn, ~p"/")
 
       html = render_hook(view, "search", %{"value" => "mountain"})
 
       assert html =~ ~s(href="/products/#{mountain.slug}")
-      assert html =~ ~s(data-phx-link="redirect")
+      assert html =~ ~s(data-phx-link="patch")
     end
 
     test "results have ARIA listbox and option roles", %{conn: conn} do