Add ASP.NET Core backend hosting business rules; FE consumes via typed client

Move the authoritative business rules off the frontend into a real backend,
realising the BFF-lite + decision-DTO design (ADR-0001) that until now lived
only in static mock JSON.

Backend (backend/):
- ASP.NET Core (.NET 10) minimal API, contract-first, Swagger UI at /swagger.
- DDD Domain/ rules layer: profession derivation + applicable policy questions
  (DiplomaRules), herregistratie eligibility + reason (HerregistratieRule),
  scholing threshold (IntakePolicy), submit rejections + reference generation
  (SubmissionRules). In-memory seeded data, ProblemDetails (RFC 7807) errors.
- 27 xUnit tests: rule units + endpoint integration incl. BRP no-address and
  DUO not-found fallbacks and 422 submit paths.

Frontend (only infrastructure/ + contracts/ change, as the architecture promised):
- NSwag-generated typed client (api-client.ts), routed through Angular HttpClient
  via a small fetch adapter so the ?scenario= interceptor still applies.
- GET adapters use resource({ loader: client.x }); submit commands call the client
  and map ProblemDetails -> err. The hardcoded uren==0 / manual-diploma rules are
  deleted (now server-side). Domain, stores, UI and format validators unchanged.
- Deleted the now-dead public/mock/*.json.

Tooling/docs:
- npm start proxies /api -> backend; npm run gen:api regenerates the client;
  docker compose up runs both (bind mounts use :z for SELinux/Fedora).
- backend/README.md walkthrough: adding a policy question is a one-file backend
  change, no FE change, no client regen. Updated CLAUDE.md + ARCHITECTURE.md.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/app/registratie/infrastructure/big-register.adapter.ts

@@ -1,19 +1,26 @@
-import { Injectable } from '@angular/core';
-import { httpResource } from '@angular/common/http';
-import { Aantekening } from '../domain/registration';
+import { Injectable, inject, resource } from '@angular/core';
+import { Aantekening, AantekeningType } from '../domain/registration';
+import { ApiClient, AantekeningDto } from '@shared/infrastructure/api-client';
 
 /**
  * Infrastructure adapter for the BIG-register source. Exposes signal-based
- * resources (Angular's httpResource); each returns a Resource with
- * status()/value()/error()/reload(). Call from an injection context
- * (a field initializer in the store).
+ * resources (Angular's `resource` over the generated typed client); each returns
+ * a Resource with status()/value()/error()/reload(). Call from an injection
+ * context (a field initializer in the store).
  *
  * Note: registration + person are now served via the aggregated dashboard-view
  * endpoint (see DashboardViewAdapter). Only the notes stream remains separate.
  */
 @Injectable({ providedIn: 'root' })
 export class BigRegisterAdapter {
+  private client = inject(ApiClient);
+
   aantekeningenResource() {
-    return httpResource<Aantekening[]>(() => 'mock/notes.json', { defaultValue: [] });
+    return resource({ loader: () => this.client.notes().then((ns) => ns.map(toAantekening)) });
   }
 }
+
+/** Map the wire DTO (all fields optional) onto our domain type. */
+function toAantekening(n: AantekeningDto): Aantekening {
+  return { type: n.type as AantekeningType, omschrijving: n.omschrijving ?? '', datum: n.datum ?? '' };
+}