Upgrade heatmaps stile Hotjar: movimenti mouse e anteprima pagina live.

Traccia i movimenti aggregati, overlay a gradienti sull’iframe della pagina e toggle click/move in admin.

Co-authored-by: Cursor <cursoragent@cursor.com>

backend/db/migrate/20260820210000_add_move_heatmap_to_analytics.rb

@@ -0,0 +1,8 @@
+# frozen_string_literal: true
+
+class AddMoveHeatmapToAnalytics < ActiveRecord::Migration[7.2]
+  def change
+    add_column :analytics_events, :weight, :integer, null: false, default: 1
+    add_column :analytics_page_cells, :move_count, :integer, null: false, default: 0
+  end
+end