feat: integrate PostHog for analytics tracking and add PostHogProvider component

lib/posthog.ts

@@ -0,0 +1,11 @@
+import { PostHog } from "posthog-node"
+
+export default function PostHogClient() {
+  const posthogClient = new PostHog(process.env.NEXT_PUBLIC_POSTHOG_KEY!, {
+    host: process.env.NEXT_PUBLIC_POSTHOG_HOST,
+    capture_pageview: 'history_change',
+    flushAt: 1,
+    flushInterval: 0,
+  })
+  return posthogClient
+}