test(portal-self-service): DigiD-guarded registration submit page (refs #67)

Scaffold libs/ui (NL Design System via Utrecht components) and libs/auth (DigiD OIDC
over angular-auth-oidc-client: mockable AuthService, provider, token interceptor,
authenticated guard). Failing component + axe tests for the RegistrationPage: it must
show the signed-in BSN, submit to the BFF (mocked api-client) and confirm, with no
WCAG 2.1 AA violations. The page is a stub, so the behaviour tests fail; green follows.

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

libs/auth/vite.config.mts

@@ -0,0 +1,28 @@
+/// <reference types='vitest' />
+import { defineConfig } from 'vite';
+import angular from '@analogjs/vite-plugin-angular';
+import { nxViteTsPaths } from '@nx/vite/plugins/nx-tsconfig-paths.plugin';
+import { nxCopyAssetsPlugin } from '@nx/vite/plugins/nx-copy-assets.plugin';
+
+export default defineConfig(() => ({
+  root: __dirname,
+  cacheDir: '../../node_modules/.vite/libs/auth',
+  plugins: [angular(), nxViteTsPaths(), nxCopyAssetsPlugin(['*.md'])],
+  // Uncomment this if you are using workers.
+  // worker: {
+  //   plugins: () => [ nxViteTsPaths() ],
+  // },
+  test: {
+    name: 'auth',
+    watch: false,
+    globals: true,
+    environment: 'jsdom',
+    include: ['{src,tests}/**/*.{test,spec}.{js,mjs,cjs,ts,mts,cts,jsx,tsx}'],
+    setupFiles: ['src/test-setup.ts'],
+    reporters: ['default'],
+    coverage: {
+      reportsDirectory: '../../coverage/libs/auth',
+      provider: 'v8' as const,
+    },
+  },
+}));