feat: replace sentry with posthog

lib/posthog-server.ts

@@ -0,0 +1,17 @@
+import { PostHog } from "posthog-node";
+
+let posthogClient: PostHog | null = null;
+
+export function getPostHogClient() {
+  if (!posthogClient) {
+    posthogClient = new PostHog(
+      process.env.NEXT_PUBLIC_POSTHOG_PROJECT_TOKEN!,
+      {
+        host: process.env.NEXT_PUBLIC_POSTHOG_HOST,
+        flushAt: 1,
+        flushInterval: 0,
+      },
+    );
+  }
+  return posthogClient;
+}