Add a language switcher matching the CIBG Taal-instellen pattern: a <nav> region
(sr-only heading + aria-label) with an endonym link per locale (lang/hreflang, the
active one aria-current + non-link), mounted right after the skip link in the shell.
Compile-time $localize means each locale is its own bundle under /<locale>/, so the
switch is a full navigation to the sibling bundle — active locale read from the baked
base href. Pure localeLinks() (+spec) builds path-preserving targets. Since `ng serve`
serves nl-only at /, add `npm run serve:i18n` (localized build + a tiny static server
with per-locale SPA fallback) so the switch is demoable. +story.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
