feat(gro-609): add Stripe details to invoice modal and fix stats date filter

- Add GET /api/invoices/:id/stripe-details endpoint to fetch card last4 and
  payment status from Stripe
- Add getPaymentIntentDetails() to payment service
- Fix stats summary query to filter by startOfMonth
- Add cardLast4, paymentStatus, stripeRefundId transient fields to Invoice type
- Display Stripe details (card last4, payment status, refund status) in modal
- Add stripeRefundId and paymentFailureReason to Invoice schema (was missing in dev types)

Ref: GRO-609
Co-Authored-By: Paperclip <noreply@paperclip.ing>

apps/api/src/services/payment.ts

@@ -162,3 +162,19 @@ export async function createSetupIntent(customerId: string): Promise<{ clientSec
 
   return { clientSecret: setupIntent.client_secret! };
 }
+
+export async function getPaymentIntentDetails(
+  paymentIntentId: string
+): Promise<{ cardLast4: string | null; paymentStatus: string | null } | null> {
+  const stripe = getStripeClient();
+  if (!stripe) return null;
+
+  const pi = await stripe.paymentIntents.retrieve(paymentIntentId);
+  const cardLast4 = pi.payment_method
+    ? (pi.payment_method as Stripe.PaymentMethod).card?.last4 ?? null
+    : null;
+  return {
+    cardLast4,
+    paymentStatus: pi.status ?? null,
+  };
+}