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>

public/cibg-huisstijl/css/tinymce/tinymce-cibg.css

@@ -0,0 +1,26 @@
+/*! Part of CIBG Huisstijl 3.22.0 */
+/**
+  Dit bestand kan optioneel gebruikt worden als je TinyMCE editors in je applicatie gebruikt.
+  Deze CSS bepaalt de styling van de content van de tinymce editors en niet controls van de editor zelf.
+ */
+body, * {
+  font-family: "Verdana", sans-serif;
+  line-height: 1.25rem;
+}
+
+p, li {
+  font-family: "Verdana", sans-serif;
+  font-size: 0.825rem;
+}
+
+p {
+  margin-top: 0;
+}
+
+h2, h3, h4 {
+  font-size: 0.825rem;
+  font-weight: bold;
+  line-height: 1.25rem;
+  margin-bottom: 0;
+  padding-bottom: 0;
+}