Rijkshuisstijl restyle + wizard fixes

Chrome: two-tier Rijksoverheid header (white brand bar + lint-blue
breadcrumb bar, route-driven), dark multi-column footer, white page
surface. Session shown via a shared SESSION_PORT token (keeps shared/
free of the auth context).

Overview ("Mijn overzicht") rebuilt to the NL Design System #392 pattern:
side-nav + "Wat moet ik regelen" task list (derived) + "Mijn registratie"
cards. New shared components: card, task-list, side-nav; pure
tasksFromProfile (+spec).

Wizards: grey form panel, connected numbered stepper, form-field
"(verplicht)" markers + styled description/error, full-width inputs.
Propagated to login, detail, change-request, address-fields.

Bug fixes:
- wizard-shell: add FormsModule so NgForm intercepts submit (wizards now
  advance; no native GET leaking choices into the URL).
- wizard-shell: error-summary links focus the field instead of navigating
  (a fragment href resolved against <base href="/"> reloaded to "/" and
  bounced to login).
- wizard-shell: error-summary focus only on the rising edge, so typing
  while errors are shown no longer scrolls the page up.

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

src/app/shared/layout/side-nav/side-nav.stories.ts

@@ -0,0 +1,27 @@
+import type { Meta, StoryObj } from '@storybook/angular';
+import { applicationConfig } from '@storybook/angular';
+import { provideRouter } from '@angular/router';
+import { SideNavComponent } from './side-nav.component';
+
+const meta: Meta<SideNavComponent> = {
+  title: 'Layout/Side Nav',
+  component: SideNavComponent,
+  decorators: [applicationConfig({ providers: [provideRouter([])] })],
+  render: (args) => ({
+    props: args,
+    template: `<div style="max-inline-size:15rem"><app-side-nav [items]="items" /></div>`,
+  }),
+};
+export default meta;
+type Story = StoryObj<SideNavComponent>;
+
+export const Default: Story = {
+  args: {
+    items: [
+      { label: 'Overzicht', to: '/dashboard' },
+      { label: 'Mijn gegevens', to: '/registratie' },
+      { label: 'Herregistratie', to: '/herregistratie' },
+      { label: 'Inschrijven', to: '/registreren' },
+    ],
+  },
+};