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>

package.json

@@ -12,6 +12,9 @@
     "@angular/forms": "21.2.9",
     "@angular/platform-browser": "21.2.9",
     "@angular/router": "21.2.9",
+    "@utrecht/component-library-angular": "^3.0.2",
+    "@utrecht/design-tokens": "^6.2.1",
+    "angular-auth-oidc-client": "^21.0.2",
     "rxjs": "~7.8.0",
     "zone.js": "0.16.0"
   },
@@ -40,11 +43,13 @@
     "@swc-node/register": "1.11.1",
     "@swc/core": "1.15.8",
     "@swc/helpers": "0.5.18",
+    "@testing-library/angular": "^19.4.1",
     "@types/node": "20.19.9",
     "@typescript-eslint/utils": "^8.40.0",
     "@vitest/coverage-v8": "~4.1.0",
     "@vitest/ui": "~4.1.0",
     "angular-eslint": "21.3.1",
+    "axe-core": "^4.12.1",
     "esbuild": "^0.27.0",
     "eslint": "^9.8.0",
     "eslint-config-prettier": "^10.0.0",
@@ -60,6 +65,7 @@
     "typescript-eslint": "^8.40.0",
     "vite": "8.0.9",
     "vite-tsconfig-paths": "^5.1.4",
-    "vitest": "~4.1.0"
+    "vitest": "~4.1.0",
+    "vitest-axe": "^0.1.0"
   }
 }