Restructure into DDD bounded contexts + functional state management

Reorganise from atomic-design-only folders into bounded contexts
(auth / registratie / herregistratie) over a shared kernel, each split into
domain / application / infrastructure / ui layers. Dependencies point inward;
the domain layer is framework-free. Path aliases (@shared/@auth/@registratie/
@herregistratie) make import direction explicit.

State management (Elm-style, native TS, no new deps):
- shared/application/store.ts — createStore(init, update): pure reducer + signal
- shared/application/remote-data.ts — add map/map2/map3/andThen combinators so
  several services fold into one RemoteData; <app-async> gains an [rd] input
- registratie/application/big-profile.store.ts — root singleton combining the
  BIG-register and BRP services via map2 into one state; holds the optimistic
  herregistratie flag shared with the dashboard
- herregistratie: machine gains a WizardMsg union + pure reduce; submit is a
  command that calls infra and dispatches the result, with optimistic update +
  rollback against the shared store
- auth: SessionStore + DigiD adapter + functional route guard; login establishes
  the session, protected routes use canActivate

Rich domain: registration.policy.ts (statusColor/label, herregistratie
eligibility, invariants); BigNummer/Postcode/Uren value objects with smart
constructors. status-badge is now domain-free (colour/label inputs).

Specs for the reducer, RemoteData combinators, and eligibility policy.

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

src/app/shared/ui/form-field/form-field.component.ts

@@ -0,0 +1,25 @@
+import { Component, input } from '@angular/core';
+
+/** Molecule: form field = label + projected control + optional error/description.
+    Reused by both the login form and the change-request form. */
+@Component({
+  selector: 'app-form-field',
+  template: `
+    <div class="rhc-form-field utrecht-form-field" [class.utrecht-form-field--invalid]="!!error()">
+      <label class="utrecht-form-label" [for]="fieldId()">{{ label() }}</label>
+      @if (description()) {
+        <div class="utrecht-form-field-description">{{ description() }}</div>
+      }
+      <ng-content />
+      @if (error()) {
+        <div class="utrecht-form-field-error-message" role="alert">{{ error() }}</div>
+      }
+    </div>
+  `,
+})
+export class FormFieldComponent {
+  label = input.required<string>();
+  fieldId = input.required<string>();
+  description = input<string>();
+  error = input<string>();
+}