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/composables/useLanding.ts

@@ -45,6 +45,14 @@ export function useLocalizeHref() {
   }
 }
 
+// Fire a custom Umami event. No-op on the server and when the tracker isn't
+// active (e.g. localhost dev, where data-domains limits it to dezky.eu).
+export function track(event: string, data?: Record<string, unknown>) {
+  if (!import.meta.client) return
+  const u = (window as unknown as { umami?: { track: (e: string, d?: unknown) => void } }).umami
+  u?.track(event, data)
+}
+
 // Smooth-scroll to an in-page anchor, accounting for the sticky 72px nav.
 // Non-anchor / placeholder links (#) are ignored.
 export function scrollToAnchor(hash: string) {