Billing Stripe, link regia mobile e staff solo trasmissione.

Aggiunge fatturazione club, pagina regia condivisibile senza account, roster squadre e rimuove la modalità controller dall'app (v1.1.0).

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

backend/app/models/billing/payment.rb

@@ -0,0 +1,25 @@
+module Billing
+  class Payment < ApplicationRecord
+    self.table_name = "billing_payments"
+
+    STATUSES = %w[paid failed refunded].freeze
+
+    belongs_to :club
+    has_one :invoice, class_name: "Billing::Invoice", foreign_key: :billing_payment_id, dependent: :nullify
+
+    validates :amount_cents, numericality: { greater_than: 0 }
+    validates :currency, presence: true
+    validates :status, inclusion: { in: STATUSES }
+    validates :stripe_invoice_id, uniqueness: true, allow_nil: true
+
+    scope :recent, -> { order(paid_at: :desc, created_at: :desc) }
+
+    def amount_euros
+      amount_cents / 100.0
+    end
+
+    def formatted_amount
+      format("%.2f €", amount_euros)
+    end
+  end
+end