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/app.routes.ts

@@ -1,5 +1,6 @@
 import { Routes } from '@angular/router';
-import { ShellComponent } from './templates/shell/shell.component';
+import { ShellComponent } from '@shared/layout/shell/shell.component';
+import { authGuard } from '@auth/auth.guard';
 
 export const routes: Routes = [
   {
@@ -7,11 +8,11 @@ export const routes: Routes = [
     component: ShellComponent, // persistent header/footer; only children swap
     children: [
       { path: '', pathMatch: 'full', redirectTo: 'login' },
-      { path: 'login', loadComponent: () => import('./pages/login/login.page').then(m => m.LoginPage) },
-      { path: 'dashboard', loadComponent: () => import('./pages/dashboard/dashboard.page').then(m => m.DashboardPage) },
-      { path: 'registratie', loadComponent: () => import('./pages/registration-detail/registration-detail.page').then(m => m.RegistrationDetailPage) },
-      { path: 'herregistratie', loadComponent: () => import('./pages/herregistratie/herregistratie.page').then(m => m.HerregistratiePage) },
-      { path: 'concepts', loadComponent: () => import('./pages/concepts/concepts.page').then(m => m.ConceptsPage) },
+      { path: 'login', loadComponent: () => import('@auth/ui/login.page').then(m => m.LoginPage) },
+      { path: 'dashboard', canActivate: [authGuard], loadComponent: () => import('@registratie/ui/dashboard.page').then(m => m.DashboardPage) },
+      { path: 'registratie', canActivate: [authGuard], loadComponent: () => import('@registratie/ui/registration-detail.page').then(m => m.RegistrationDetailPage) },
+      { path: 'herregistratie', canActivate: [authGuard], loadComponent: () => import('@herregistratie/ui/herregistratie.page').then(m => m.HerregistratiePage) },
+      { path: 'concepts', loadComponent: () => import('./showcase/concepts.page').then(m => m.ConceptsPage) },
       { path: '**', redirectTo: 'login' },
     ],
   },