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/layout.tsx

@@ -3,6 +3,7 @@ import { Cormorant_Garamond, Mulish } from 'next/font/google'
 import './globals.css'
 import Nav from '@/components/ui/Nav'
 import Footer from '@/components/ui/Footer'
+import PostHogProvider from '@/components/PostHogProvider'
 
 const cormorant = Cormorant_Garamond({
   subsets: ['latin'],
@@ -45,9 +46,11 @@ export default function RootLayout({
             backgroundImage: `url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='200' height='200'%3E%3Cfilter id='n'%3E%3CfeTurbulence type='fractalNoise' baseFrequency='0.85' numOctaves='3' stitchTiles='stitch'/%3E%3C/filter%3E%3Crect width='100%25' height='100%25' filter='url(%23n)'/%3E%3C/svg%3E")`,
           }}
         />
-        <Nav />
-        <main>{children}</main>
-        <Footer />
+        <PostHogProvider>
+          <Nav />
+          <main>{children}</main>
+          <Footer />
+        </PostHogProvider>
       </body>
     </html>
   )