Add PostHog analytics — full event tracking across all pages

Tracks pageviews, hero/CTA clicks, product teaser clicks, app card
and detail views, newsletter signups, nav interactions, and footer
link clicks with structured properties for PostHog dashboards.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

app/apps/page.tsx

@@ -1,10 +1,7 @@
-import type { Metadata } from 'next'
-import Link from 'next/link'
+'use client'
 
-export const metadata: Metadata = {
-  title: 'Apps – HyggeCraftery',
-  description: 'Drei sanfte Apps für einen langsameren, bewussteren Alltag.',
-}
+import Link from 'next/link'
+import { posthog } from '@/lib/posthog'
 
 const apps = [
   {
@@ -56,6 +53,7 @@ export default function AppsPage() {
             <Link
               key={app.name}
               href={app.href}
+              onClick={() => posthog.capture('app_card_clicked', { app_name: app.name })}
               style={{
                 textDecoration: 'none',
                 display: 'grid',