feat(website): bilingual i18n (English default, Danish at /da) + SEO

Add @nuxtjs/i18n: English is the default locale (no prefix), Danish lives
under /da (prefix_except_default). Both server-rendered and indexed with
hreflang alternates + per-locale canonical (useLocaleHead in app.vue).
First-visit browser language is auto-detected and remembered in the
i18n_redirected cookie (redirectOn root).

- Keep the hand-authored COPY object; useLang/useCopy now read the i18n
  locale; useLocalizeHref/useLangToggle added. Every internal link is
  localized so navigation stays in-locale.
- Clear segmented EN|DA language switcher (active segment filled) replacing
  the ambiguous "en · da" pill.
- SEO: useSeoMeta defaults are locale-aware; og:image switches per locale
  (English / Danish share card); favicon links; robots.txt + sitemap.xml;
  env-aware siteUrl/baseUrl (localhost in dev, dezky.eu in prod).
- Update the cookie policy (dezky-lang -> i18n_redirected).
- Gate the Traefik wss:443 HMR behind DEZKY_TRAEFIK so localhost dev/DevTools
  connect over plain ws (fixes the DevTools disconnect loop).

apps/website/components/landing/Hero.vue

@@ -8,6 +8,7 @@ import { useTheme, useCopy } from '~/composables/useLanding'
 
 const t = useTheme()
 const copy = useCopy()
+const localePath = useLocalePath()
 
 // Variant A is the production default the user landed on.
 const headline = computed(() => copy.value.hero.headlineA)
@@ -46,7 +47,7 @@ const brush = {
       </div>
 
       <div :style="{ display: 'flex', gap: '12px', marginTop: '40px', flexWrap: 'wrap' }">
-        <LandingBtn variant="primary" size="lg" @click="navigateTo('/demo')">{{ copy.hero.cta }} →</LandingBtn>
+        <LandingBtn variant="primary" size="lg" @click="navigateTo(localePath('/demo'))">{{ copy.hero.cta }} →</LandingBtn>
         <LandingBtn variant="secondary" size="lg">{{ copy.hero.sub_cta }}</LandingBtn>
       </div>