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>

package.json

@@ -0,0 +1,64 @@
+{
+  "name": "register-referentie",
+  "version": "0.0.0",
+  "license": "MIT",
+  "scripts": {},
+  "private": true,
+  "dependencies": {
+    "@angular-devkit/build-angular": "21.2.7",
+    "@angular/common": "21.2.9",
+    "@angular/compiler": "21.2.9",
+    "@angular/core": "21.2.9",
+    "@angular/forms": "21.2.9",
+    "@angular/platform-browser": "21.2.9",
+    "@angular/router": "21.2.9",
+    "rxjs": "~7.8.0",
+    "zone.js": "0.16.0"
+  },
+  "devDependencies": {
+    "@analogjs/vite-plugin-angular": "2.2.0",
+    "@analogjs/vitest-angular": "2.2.0",
+    "@angular-devkit/core": "21.2.7",
+    "@angular-devkit/schematics": "21.2.7",
+    "@angular/build": "21.2.7",
+    "@angular/cli": "21.2.7",
+    "@angular/compiler-cli": "21.2.9",
+    "@angular/language-service": "21.2.9",
+    "@eslint/js": "^9.8.0",
+    "@nx/angular": "23.0.1",
+    "@nx/devkit": "23.0.1",
+    "@nx/esbuild": "23.0.1",
+    "@nx/eslint": "23.0.1",
+    "@nx/eslint-plugin": "23.0.1",
+    "@nx/js": "23.0.1",
+    "@nx/vite": "23.0.1",
+    "@nx/vitest": "23.0.1",
+    "@nx/web": "23.0.1",
+    "@nx/workspace": "23.0.1",
+    "@oxc-project/runtime": "^0.115.0",
+    "@schematics/angular": "21.2.7",
+    "@swc-node/register": "1.11.1",
+    "@swc/core": "1.15.8",
+    "@swc/helpers": "0.5.18",
+    "@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",
+    "esbuild": "^0.27.0",
+    "eslint": "^9.8.0",
+    "eslint-config-prettier": "^10.0.0",
+    "jiti": "2.4.2",
+    "jsdom": "~22.1.0",
+    "jsonc-eslint-parser": "^2.1.0",
+    "nx": "23.0.1",
+    "prettier": "^3.8.1",
+    "ts-node": "10.9.1",
+    "tslib": "^2.3.0",
+    "typescript": "~5.9.2",
+    "typescript-eslint": "^8.40.0",
+    "vite": "8.0.9",
+    "vite-tsconfig-paths": "^5.1.4",
+    "vitest": "~4.1.0"
+  }
+}