Add PostHog, move Plausible to v4, and drop Sentry session replay

PostHog loads after the page is idle through a same-origin /ingest proxy and follows the signed-in Convex user. Plausible uses the per-site script through a /pa proxy. Sentry keeps errors and traces only. Pages load only the @gib/ui modules they import, and client code reads public env from publicEnv.ts so zod stays out of the browser.

apps/next/src/instrumentation-client.ts

@@ -1,27 +1,35 @@
 // https://docs.sentry.io/platforms/javascript/guides/nextjs/
-import { env } from '@/env';
+import { startAnalytics } from '@/lib/analytics';
+import { publicEnv } from '@/publicEnv';
 import * as Sentry from '@sentry/nextjs';
 
+// Session replay is left to PostHog, so Sentry carries no replay integration.
 Sentry.init({
-  dsn: env.NEXT_PUBLIC_SENTRY_DSN,
-  integrations: [
-    Sentry.replayIntegration({
-      maskAllText: false,
-      blockAllMedia: false,
-    }),
-    Sentry.feedbackIntegration({
-      colorScheme: 'system',
-    }),
-  ],
+  dsn: publicEnv.NEXT_PUBLIC_SENTRY_DSN,
   // https://docs.sentry.io/platforms/javascript/guides/nextjs/configuration/options/#sendDefaultPii
-  sendDefaultPii: true,
+  sendDefaultPii: false,
   // https://docs.sentry.io/platforms/javascript/configuration/options/#traces-sample-rate
-  tracesSampleRate: 1,
+  // A tenth of page loads is plenty for performance trends and keeps the
+  // self-hosted Sentry light.
+  tracesSampleRate: 0.1,
   enableLogs: true,
-  // https://docs.sentry.io/platforms/javascript/session-replay/configuration/#general-integration-configuration
-  replaysSessionSampleRate: 0.5,
-  replaysOnErrorSampleRate: 1.0,
   debug: false,
 });
+
+// The feedback widget is a floating button nobody needs during the first
+// paint, so its code is split into its own chunk and added once the page has
+// loaded.
+const addFeedbackWidget = async () => {
+  const { feedbackIntegration } = await import('@sentry/nextjs');
+  Sentry.addIntegration(feedbackIntegration({ colorScheme: 'system' }));
+};
+if (document.readyState === 'complete') void addFeedbackWidget();
+else
+  window.addEventListener('load', () => void addFeedbackWidget(), {
+    once: true,
+  });
+
+startAnalytics();
+
 // `captureRouterTransitionStart` is available from SDK version 9.12.0 onwards
 export const onRouterTransitionStart = Sentry.captureRouterTransitionStart;