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/orval.config.ts

@@ -0,0 +1,17 @@
+import { defineConfig } from 'orval';
+
+// Generates the BFF client (Angular HttpClient service + models) from the committed
+// OpenAPI contract. Never hand-edit the generated output — re-run `nx run api-client:generate`
+// after the BFF spec changes (CLAUDE.md §10; docs/frontend-decisions.md).
+export default defineConfig({
+  bff: {
+    input: '../../services/bff/openapi.json',
+    output: {
+      target: './src/lib/generated/bff-api.ts',
+      client: 'angular',
+      mode: 'single',
+      clean: true,
+      prettier: true,
+    },
+  },
+});