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/spec/services/billing/stripe/invoice_payment_refs_spec.rb

@@ -0,0 +1,20 @@
+require "rails_helper"
+
+RSpec.describe Billing::Stripe::InvoicePaymentRefs do
+  it "legge payment_intent dalla raccolta payments (API Basil+)" do
+    pi = double(id: "pi_new")
+    payment = double(payment_intent: pi)
+    invoice = double(
+      payments: double(data: [double(payment: payment)])
+    )
+
+    expect(described_class.payment_intent_id(invoice)).to eq("pi_new")
+    expect(described_class.charge_id(invoice)).to be_nil
+  end
+
+  it "non accede a payment_intent top-level sull'invoice" do
+    invoice = double(payments: double(data: []))
+    expect(invoice).not_to receive(:payment_intent)
+    expect(described_class.payment_intent_id(invoice)).to be_nil
+  end
+end