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>

CLAUDE.md

@@ -8,15 +8,20 @@ update this file.
 
 POC of a Dutch BIG-register self-service portal (healthcare professionals log in,
 view their registration, apply for re-registration). Angular 22, standalone,
-signals. No real backend/auth — static mock JSON + fake timers.
+signals. Auth is faked; **data and business rules are served by a minimal ASP.NET
+Core backend** (`backend/`, see its README — in-memory seeded, no DB) and consumed
+through an NSwag-generated typed client. The FE renders the backend's decisions.
 
 ## Commands
 
 ```bash
-npm start          # ng serve → http://localhost:4200
+npm start          # ng serve (proxies /api → backend) → http://localhost:4200
 npm test           # vitest
 npm run build      # ng build (must stay green)
 npm run storybook  # component library by atomic layer
+npm run gen:api    # regenerate the typed client from the backend OpenAPI doc
+docker compose up  # run FE + backend together (Swagger at :5000/swagger)
+cd backend && dotnet test   # backend rule + endpoint tests
 ```
 
 `.npmrc` sets `legacy-peer-deps=true` (Storybook's peer range lags Angular 22).