Billing: fatture manuali, profilo obbligatorio e piani Stripe mensile/annuale.

Rimuove link al portale Stripe in area cliente, aggiunge flusso admin per PDF
fattura e email, blocca checkout senza dati di fatturazione, allinea prezzi
a €4,90/€39,90 e €9,90/€69,90, locale italiano e documentazione deploy.

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

backend/app/services/billing/stripe/invoice_metadata.rb

@@ -0,0 +1,41 @@
+module Billing
+  module Stripe
+    # Metadati e subscription id su Invoice (API Basil+: parent.subscription_details).
+    module InvoiceMetadata
+      module_function
+
+      def merged(invoice)
+        base = metadata_hash(invoice)
+        base.merge(subscription_metadata(invoice))
+      end
+
+      def subscription_metadata(invoice)
+        details = subscription_details(invoice)
+        return {} if details.blank?
+
+        metadata_hash(details)
+      end
+
+      def subscription_id(invoice)
+        details = subscription_details(invoice)
+        return nil if details.blank?
+
+        InvoicePaymentRefs.safe_get(details, :subscription)
+      end
+
+      def subscription_details(invoice)
+        parent = InvoicePaymentRefs.safe_get(invoice, :parent)
+        return nil if parent.blank?
+
+        InvoicePaymentRefs.safe_get(parent, :subscription_details)
+      end
+
+      def metadata_hash(obj)
+        meta = InvoicePaymentRefs.safe_get(obj, :metadata)
+        meta.to_h.stringify_keys
+      rescue NoMethodError
+        {}
+      end
+    end
+  end
+end