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.test.tsx

@@ -100,6 +100,33 @@ describe('PatientDetailPage (پرونده تب‌دار)', () => {
     expect(await screen.findByText('اطلاعات فاکتور')).toBeInTheDocument();
   });
 
+  it('issues the invoice first (create + finalize) when the paid session has none', async () => {
+    const base = get.getMockImplementation()!;
+    get.mockImplementation((url: string) => {
+      if (url === '/api/v1/patient/r1/sessions') return Promise.resolve({ success: true, data: [
+        { uuid: 's3', services: [{ service_name: 'لیزر' }], doctor_name: 'دکتر فتحی', final_price_rials: 1000000, is_paid: true, patient_debt_rials: 0, created_at: 1700000000, visit_price_rials: 0 },
+      ], meta: { totalRecords: 1 } });
+      if (url === '/api/v1/billing/invoices/iv9') return Promise.resolve({ success: true, data: { data: {
+        uuid: 'iv9', status: 'finalized', issued_at: 1700000000, total_rials: 1000000,
+        base_insurance_rials: 0, supplementary_rials: 0, patient_rials: 1000000, items: [],
+      } } });
+      return base(url);
+    });
+    const post = api.post as ReturnType<typeof vi.fn>;
+    post.mockReset();
+    post.mockImplementation((url: string) => {
+      if (url === '/api/v1/billing/invoices') return Promise.resolve({ success: true, data: { data: { uuid: 'iv9', status: 'draft' } } });
+      return Promise.resolve({ success: true, data: {} });
+    });
+
+    renderDetail();
+    fireEvent.click(await screen.findByText('مشاهده فاکتور'));
+
+    await waitFor(() => expect(post).toHaveBeenCalledWith('/api/v1/billing/invoices', { session_uuid: 's3' }));
+    expect(post).toHaveBeenCalledWith('/api/v1/billing/invoices/iv9/finalize', {});
+    expect(await screen.findByText('خلاصه فاکتور')).toBeInTheDocument();
+  });
+
   it('renders the editable «اطلاعات پرونده» form prefilled from the profile', async () => {
     renderDetail();
     await loaded();