test(portal-self-service): self-service portal placeholder renders (refs #65)

Bootstrap the Nx (pnpm) workspace at the repo root with the self-service Angular
app (standalone + signals, Vitest via @angular/build, ESLint) — the frontend
foundation. Nx is scoped to apps/+libs/ only; the .NET services stay on
dotnet/Makefile (no @nx/docker inference). A failing test asserts the app renders
a 'Zelfservice' heading; it still shows the generated Nx welcome page, so it fails.
Green commit implements the placeholder.

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

apps/self-service/src/app/app.spec.ts

@@ -0,0 +1,17 @@
+import { TestBed } from '@angular/core/testing';
+import { App } from './app';
+
+describe('App', () => {
+  beforeEach(async () => {
+    await TestBed.configureTestingModule({
+      imports: [App],
+    }).compileComponents();
+  });
+
+  it('renders the self-service portal heading', async () => {
+    const fixture = TestBed.createComponent(App);
+    await fixture.whenStable();
+    const compiled = fixture.nativeElement as HTMLElement;
+    expect(compiled.querySelector('h1')?.textContent).toContain('Zelfservice');
+  });
+});