feat(design): re-theme to CIBG Huisstijl (Bootstrap 5.2), replacing RHC/Utrecht

The portal now adheres to the CIBG design system (designsystem.cibg.nl) — a customized
Bootstrap 5.2 build — replacing the Rijkshuisstijl-Community / Utrecht theme. See ADR-0003.

- Vendor @cibg/huisstijl@3.22.0 under public/cibg-huisstijl/, loaded via a <link> in
  index.html (Storybook serves it via staticDirs). Drop the two @rijkshuisstijl-community deps.
- Token bridge in styles.scss: redefine the app's ~54 --rhc-* tokens onto CIBG/--bs-* values,
  so components keep referencing tokens (no 300+ site rewrite). System-font stack; licensed
  RO/Rijks text fonts intentionally not shipped.
- Re-skin every shared atom to Bootstrap/CIBG classes (btn, form-control, form-check-*,
  table, breadcrumb, …) keeping their input() APIs. alert is hand-rolled (CIBG drops .alert);
  local .card/.badge renamed to avoid Bootstrap collisions.
- Domain pages: drop stray rhc-*/utrecht-* classes; registration-table → table table-striped.

Verified: build green, check:tokens OK, lint clean, 174 tests pass, build-storybook OK,
and the served build loads the vendored CSS (200, .btn-primary present).

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

src/app/shared/ui/button/button.component.ts

@@ -2,19 +2,18 @@ import { Component, input } from '@angular/core';
 
 type Variant = 'primary' | 'secondary' | 'subtle' | 'danger';
 
-/** Atom: button. Thin wrapper over the Utrecht/RHC button CSS. */
+/** Atom: button. Thin wrapper over the CIBG/Bootstrap button CSS. */
 @Component({
   selector: 'app-button',
   template: `
     <button
       [type]="type()"
       [disabled]="disabled()"
-      class="utrecht-button rhc-button"
-      [class.utrecht-button--primary-action]="variant() === 'primary'"
-      [class.utrecht-button--secondary-action]="variant() === 'secondary'"
-      [class.utrecht-button--subtle]="variant() === 'subtle'"
-      [class.utrecht-button--danger]="variant() === 'danger'"
-      [class.utrecht-button--disabled]="disabled()">
+      class="btn"
+      [class.btn-primary]="variant() === 'primary'"
+      [class.btn-outline-primary]="variant() === 'secondary'"
+      [class.btn-link]="variant() === 'subtle'"
+      [class.btn-danger]="variant() === 'danger'">
       <ng-content />
     </button>
   `,