feat(portal-openbaar): surface the citizen reference in the public register (refs #78)

The BFF's public view exposes id/status/reference (never bsn/naam) and searches by
id or reference; the openbaar register's Referentie column and search now show the
reference the citizen saw on submit. api-client + openapi.json regenerated.

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

apps/openbaar/src/app/register/register-page.html

@@ -43,7 +43,7 @@
         <tbody>
           @for (entry of entries(); track entry.id) {
             <tr>
-              <td>{{ entry.id }}</td>
+              <td>{{ entry.reference }}</td>
               <td>{{ entry.status }}</td>
             </tr>
           }

apps/openbaar/src/app/register/register-page.spec.ts

@@ -5,8 +5,8 @@ import { axe } from 'vitest-axe';
 import { RegisterPage } from './register-page';
 
 const sample: OpenbaarEntry[] = [
-  { id: 'zaak-abc', status: 'INGEDIEND' },
-  { id: 'zaak-def', status: 'INGESCHREVEN' },
+  { id: 'zaak-abc', status: 'INGEDIEND', reference: 'REG-abc' },
+  { id: 'zaak-def', status: 'INGESCHREVEN', reference: 'REG-def' },
 ];
 
 function providers(get = vi.fn().mockReturnValue(of(sample))) {
@@ -22,9 +22,11 @@ describe('RegisterPage', () => {
     await render(RegisterPage, { providers: providers(get).providers });
 
     expect(get).toHaveBeenCalled();
-    expect(await screen.findByText(/zaak-abc/)).toBeTruthy();
+    // The Referentie column shows the citizen's reference (matches the submit confirmation, #78),
+    // not the internal zaak id.
+    expect(await screen.findByText(/REG-abc/)).toBeTruthy();
     expect(screen.getByText(/INGEDIEND/)).toBeTruthy();
-    expect(screen.getByText(/zaak-def/)).toBeTruthy();
+    expect(screen.getByText(/REG-def/)).toBeTruthy();
   });
 
   it('searches by the entered term', async () => {