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/invoice.rb

@@ -0,0 +1,43 @@
+module Billing
+  class Invoice < ApplicationRecord
+    self.table_name = "billing_invoices"
+
+    STATUSES = %w[draft issued sent cancelled].freeze
+    SOURCES = %w[aruba manual].freeze
+
+    belongs_to :club
+    belongs_to :billing_payment, class_name: "Billing::Payment", optional: true
+    has_one_attached :pdf
+
+    validates :number, presence: true, uniqueness: { scope: :club_id }
+    validates :issued_on, presence: true
+    validates :amount_cents, numericality: { greater_than: 0 }
+    validates :currency, presence: true
+    validates :status, inclusion: { in: STATUSES }
+    validates :source, inclusion: { in: SOURCES }
+    validate :pdf_present_when_issued
+
+    scope :recent, -> { order(issued_on: :desc, created_at: :desc) }
+
+    def amount_euros
+      amount_cents / 100.0
+    end
+
+    def formatted_amount
+      format("%.2f €", amount_euros)
+    end
+
+    def downloadable?
+      pdf.attached?
+    end
+
+    private
+
+    def pdf_present_when_issued
+      return unless status.in?(%w[issued sent])
+      return if pdf.attached?
+
+      errors.add(:pdf, "è obbligatorio per le fatture emesse")
+    end
+  end
+end