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>

packages/types/src/index.ts

@@ -159,6 +159,9 @@ export interface Invoice {
   createdAt: string;
   updatedAt: string;
   lineItems?: InvoiceLineItem[];
+  // Transient fields populated from Stripe API (not stored in DB)
+  cardLast4?: string | null;
+  paymentStatus?: string | null;
   tipSplits?: InvoiceTipSplit[];
 }