test(api-client): generated BFF client is exposed and calls the endpoints (refs #66)

Scaffold libs/api-client (Nx Angular lib) and generate a typed HttpClient client
from services/bff/openapi.json with orval (node-based; Angular target integrates
with HttpClient interceptors for the S-08c auth token). A failing test drives the
public API: it expects an injectable BffApiV1Service to POST /self-service/registrations
and GET /openbaar/register (via HttpClientTesting), but the lib barrel doesn't export
the client yet, so it fails. Normalise the vitest target to 'test'. Green exposes it.

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

libs/api-client/tsconfig.spec.json

@@ -0,0 +1,29 @@
+{
+  "extends": "./tsconfig.json",
+  "compilerOptions": {
+    "outDir": "../../dist/out-tsc",
+    "types": [
+      "vitest/globals",
+      "vitest/importMeta",
+      "vite/client",
+      "node",
+      "vitest"
+    ]
+  },
+  "include": [
+    "vite.config.ts",
+    "vite.config.mts",
+    "vitest.config.ts",
+    "vitest.config.mts",
+    "src/**/*.test.ts",
+    "src/**/*.spec.ts",
+    "src/**/*.test.tsx",
+    "src/**/*.spec.tsx",
+    "src/**/*.test.js",
+    "src/**/*.spec.js",
+    "src/**/*.test.jsx",
+    "src/**/*.spec.jsx",
+    "src/**/*.d.ts"
+  ],
+  "files": ["src/test-setup.ts"]
+}