Admin analytics: heatmap per device, anteprima staff e analisi costi.

Separa heatmap mobile/desktop, opt-out analytics per operatori, dashboard costi con KPI e trend mensili.

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

backend/app/views/admin/cost_entries/new.html.erb

@@ -0,0 +1,9 @@
+<% content_for :body_class, "admin-body" %>
+
+<div class="admin-page-head">
+  <h2 class="admin-page-title"><%= t("admin.costs.entries.new_title") %></h2>
+</div>
+
+<section class="panel">
+  <%= render "form", url: admin_cost_entries_path, method: :post %>
+</section>