fix: issue invoice on demand so view-invoice buttons actually work

The admin SPA never called POST /billing/invoices, so every session had
invoice_uuid = null and the view-invoice buttons on the patient services
tab (and MyPatients visit modal) were permanently disabled. Add a shared
useIssueInvoice hook (idempotent create + finalize when draft) and wire
it into:
- DetailsStep: the wizard's final step now really issues the invoice
- SessionServiceCard / PatientDetailPage: clicking view-invoice on a
  session without an invoice issues it first, then opens the summary
- MyPatientsPage visit modal: same, replacing the dead disabled button

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

assets/admin/pages/PatientDetailPage.tsx

@@ -22,6 +22,7 @@ import ConfirmDialog from '../components/ui/ConfirmDialog';
 import PersianDateInput from '../components/ui/PersianDateInput';
 import PatientCaseBanner, { Breadcrumb } from '../components/PatientCaseBanner';
 import SessionServiceCard, { type SessionCardData } from '../components/SessionServiceCard';
+import { useIssueInvoice } from '../hooks/useIssueInvoice';
 import AppointmentTurnCard, { type AppointmentCardData } from '../components/AppointmentTurnCard';
 import SessionPaymentAccordion, { type SessionPaymentData } from '../components/SessionPaymentAccordion';
 import InvoiceSummaryModal from '../components/InvoiceSummaryModal';
@@ -81,6 +82,16 @@ export default function PatientDetailPage() {
   const nav = useNavigate();
   const [invoiceUuid, setInvoiceUuid] = useState<string | null>(null);
 
+  // «مشاهده فاکتور»: اگر session هنوز فاکتور ندارد، اول صادر می‌شود (idempotent).
+  const issueInvoiceMut = useIssueInvoice(uuid);
+  const viewInvoice = (s: SessionCardData) => {
+    if (s.invoice_uuid) { setInvoiceUuid(s.invoice_uuid); return; }
+    issueInvoiceMut.mutate(s.uuid, {
+      onSuccess: (iv) => setInvoiceUuid(iv),
+      onError: () => toast.error('صدور فاکتور ناموفق بود'),
+    });
+  };
+
   // ── فرم «اطلاعات پرونده» (اینلاین، معادل tauri FileInfoSection) ──────────────
   // استان/شهر (Location) و بیمهٔ پایه (insurance-pricing) برای گزینه‌های فرم.
   const [editProvinceId, setEditProvinceId] = useState<number | null>(null);
@@ -217,7 +228,7 @@ export default function PatientDetailPage() {
           ) : (
             <div style={{ display: 'grid', gridTemplateColumns: 'repeat(auto-fit, minmax(240px, 1fr))', columnGap: 6, rowGap: 10, alignItems: 'stretch' }}>
               {sessions.map((s) => (
-                <SessionServiceCard key={s.uuid} session={s} onSettle={(u) => nav(`/admin/patients/${uuid}/session/${u}/pay`)} onViewInvoice={(iv) => setInvoiceUuid(iv)} />
+                <SessionServiceCard key={s.uuid} session={s} onSettle={(u) => nav(`/admin/patients/${uuid}/session/${u}/pay`)} onViewInvoice={viewInvoice} issuing={issueInvoiceMut.isPending} />
               ))}
             </div>
           )}