Rework PostHog setup — use Next.js ingest proxy + posthog-js/react

Mirrors the proven pattern from gendersloty: rewrites /ingest/* to
the PostHog host so requests go through the same origin (no CORS,
no ad-blocker issues). Uses PostHogProvider and usePostHog from
posthog-js/react official React integration.

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

next.config.mjs

@@ -1,4 +1,22 @@
 /** @type {import('next').NextConfig} */
-const nextConfig = {};
+const nextConfig = {
+  async rewrites() {
+    return [
+      {
+        source: '/ingest/static/:path*',
+        destination: 'https://analytics.hyggecraftery.com/static/:path*',
+      },
+      {
+        source: '/ingest/:path*',
+        destination: 'https://analytics.hyggecraftery.com/:path*',
+      },
+      {
+        source: '/ingest/decide',
+        destination: 'https://analytics.hyggecraftery.com/decide',
+      },
+    ]
+  },
+  skipTrailingSlashRedirect: true,
+}
 
-export default nextConfig;
+export default nextConfig