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/hooks/useIssueInvoice.ts

@@ -0,0 +1,29 @@
+import { useMutation, useQueryClient } from '@tanstack/react-query';
+import { api } from '../lib/api';
+
+interface InvoicePayload { uuid: string; status: string }
+
+/**
+ * صدور فاکتور یک مراجعه: ساخت idempotent (`POST /billing/invoices`) و سپس
+ * نهایی‌سازی draft. خروجی mutation، uuid فاکتور است تا caller مودال «خلاصه
+ * فاکتور» را باز کند. با recordUuid، لیست sessions همان بیمار invalidate
+ * می‌شود تا invoice_uuid کارت‌ها به‌روز شود.
+ */
+export function useIssueInvoice(recordUuid?: string) {
+  const qc = useQueryClient();
+
+  return useMutation({
+    mutationFn: async (sessionUuid: string): Promise<string> => {
+      const res = await api.post<any>('/api/v1/billing/invoices', { session_uuid: sessionUuid });
+      const invoice = ((res as any)?.data?.data ?? (res as any)?.data) as InvoicePayload;
+      if (invoice.status === 'draft') {
+        await api.post(`/api/v1/billing/invoices/${invoice.uuid}/finalize`, {});
+      }
+      return invoice.uuid;
+    },
+    onSuccess: () => {
+      if (recordUuid) qc.invalidateQueries({ queryKey: ['patient-sessions', recordUuid] });
+      qc.invalidateQueries({ queryKey: ['invoice'] });
+    },
+  });
+}