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/pages/demo.vue

@@ -3,7 +3,7 @@
 // info@dezky.eu (zero backend, no US tools). Swap this for the self-built
 // embedded scheduler later — the copy + layout can stay.
 import { ref, computed } from 'vue'
-import { useTheme, useCopy } from '~/composables/useLanding'
+import { useTheme, useCopy, track } from '~/composables/useLanding'
 
 definePageMeta({ layout: 'page' })
 
@@ -28,6 +28,7 @@ function submit() {
     '',
     message.value,
   ].join('\n')
+  track('demo-request', { teamSize: team.value })
   window.location.href = `mailto:info@dezky.eu?subject=${encodeURIComponent(subject)}&body=${encodeURIComponent(body)}`
 }