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/db/migrate/20260828180000_create_platform_cost_entries.rb

@@ -0,0 +1,17 @@
+# frozen_string_literal: true
+
+class CreatePlatformCostEntries < ActiveRecord::Migration[7.2]
+  def change
+    create_table :platform_cost_entries, id: :uuid do |t|
+      t.date :month, null: false
+      t.string :label, null: false, default: "Piattaforma produzione"
+      t.integer :amount_cents, null: false
+      t.text :notes
+
+      t.timestamps
+    end
+
+    add_index :platform_cost_entries, :month
+    add_index :platform_cost_entries, %i[month label]
+  end
+end