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/shared/layout/wizard-shell/wizard-shell.stories.ts

@@ -0,0 +1,37 @@
+import type { Meta, StoryObj } from '@storybook/angular';
+import { WizardShellComponent } from './wizard-shell.component';
+
+const meta: Meta<WizardShellComponent> = {
+  title: 'Templates/WizardShell',
+  component: WizardShellComponent,
+  render: (args) => ({
+    props: args,
+    template: `
+      <app-wizard-shell
+        [steps]="steps" [current]="current" [stepTitle]="stepTitle" [status]="status"
+        [primaryLabel]="primaryLabel" [canGoBack]="canGoBack" [errors]="errors" [errorMessage]="errorMessage">
+        <p class="rhc-paragraph">Voorbeeld-stapinhoud (de stapvelden worden hier geprojecteerd).</p>
+        <div wizardSuccess><p class="rhc-paragraph">Uw aanvraag is ontvangen.</p></div>
+      </app-wizard-shell>`,
+  }),
+};
+export default meta;
+type Story = StoryObj<WizardShellComponent>;
+
+const steps = ['Adres', 'Beroep', 'Controle'];
+const base = { steps, current: 1, stepTitle: 'Beroep op basis van uw diploma', primaryLabel: 'Volgende', canGoBack: true, errors: [], errorMessage: '' };
+
+export const Editing: Story = { args: { ...base, status: 'editing' } };
+export const EditingMetFouten: Story = {
+  args: {
+    ...base,
+    status: 'editing',
+    errors: [
+      { id: 'uren', message: 'Vul het aantal gewerkte uren in.' },
+      { id: 'diploma', message: 'Kies een diploma.' },
+    ],
+  },
+};
+export const Submitting: Story = { args: { ...base, status: 'submitting' } };
+export const Submitted: Story = { args: { ...base, status: 'submitted' } };
+export const Failed: Story = { args: { ...base, status: 'failed', errorMessage: 'Het indienen is niet gelukt: netwerkfout.' } };