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>

lib/posthog.ts

@@ -0,0 +1,13 @@
+import posthog from 'posthog-js'
+
+export function initPostHog() {
+  if (typeof window !== 'undefined' && !posthog.__loaded) {
+    posthog.init('phc_BHgg9S7CQqVShe7EMCdi86PxA49qcNaTsR9Nn5EGxRCT', {
+      api_host: 'https://analytics.hyggecraftery.com',
+      capture_pageview: false,
+      persistence: 'localStorage',
+    })
+  }
+}
+
+export { posthog }