- useSeoLabels(): the L8 dictionary (en, pl) of the page's content locale
(resolve locale, then html_lang, then en), overridable and extendable in
app.config.ts under seo.labels; no i18n dependency
- seo-tokens.css (spacing, colour, small type, breadcrumb separator) and
seo-base.css (.seo-visually-hidden, the focus ring of layer links), loaded
before the app's CSS and styling only .seo-* classes
