feat(website): Umami analytics (conversion + CTA events)

Add the Umami tracker (cookieless, no consent banner) in the document head,
limited to the production hostnames via data-domains so dev traffic doesn't
pollute the stats. Pageviews are auto-tracked per page and locale.

Custom events on the key funnel:
- demo-request (demo form submit, with teamSize)
- partner-application (partner form submit, with type)
- book-demo (every "Book a demo" CTA click) via data-umami-event
- login (clicks through to the app)

Also fix the mobile nav menu links, which weren't localized (would drop
Danish visitors back to English).

apps/website/components/landing/Hero.vue

@@ -47,7 +47,7 @@ const brush = {
       </div>
 
       <div :style="{ display: 'flex', gap: '12px', marginTop: '40px', flexWrap: 'wrap' }">
-        <LandingBtn variant="primary" size="lg" @click="navigateTo(localePath('/demo'))">{{ copy.hero.cta }} →</LandingBtn>
+        <LandingBtn variant="primary" size="lg" data-umami-event="book-demo" @click="navigateTo(localePath('/demo'))">{{ copy.hero.cta }} →</LandingBtn>
         <LandingBtn variant="secondary" size="lg">{{ copy.hero.sub_cta }}</LandingBtn>
       </div>