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/herregistratie/application/submit-intake.ts

@@ -1,14 +1,18 @@
 import { Result, ok, err } from '@shared/kernel/fp';
 import { ValidIntake } from '../domain/intake.machine';
+import { ApiClient } from '@shared/infrastructure/api-client';
+import { problemDetail } from '@shared/infrastructure/api-error';
 
 /**
- * Command: send the intake questionnaire to the backend. Returns a Result so the
- * caller branches on success/failure without try/catch. ponytail: faked with a
- * timer; swap for a real POST when there's an API. The "uren must be > 0" rule
- * lets the demo show the failure path.
+ * Command: POST the intake questionnaire to the backend (`/api/intakes`). The
+ * "uren must be > 0" rule now lives server-side; the backend returns a 422
+ * ProblemDetails on rejection, which we surface as the error.
  */
-export async function submitIntake(data: ValidIntake): Promise<Result<string, void>> {
-  await new Promise((r) => setTimeout(r, 800));
-  if (data.uren === 0) return err('Aanvraag afgewezen: geen gewerkte uren geregistreerd.');
-  return ok(undefined);
+export async function submitIntake(client: ApiClient, data: ValidIntake): Promise<Result<string, void>> {
+  try {
+    await client.intakes({ uren: data.uren });
+    return ok(undefined);
+  } catch (e) {
+    return err(problemDetail(e, 'Het indienen is niet gelukt. Probeer het later opnieuw.'));
+  }
 }