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/next.config.js

@@ -3,12 +3,16 @@ import { createJiti } from 'jiti';
 import { withPlausibleProxy } from 'next-plausible';
 
 const jiti = createJiti(import.meta.url);
-await jiti.import('./src/env');
+const { env } = /** @type {typeof import('./src/env')} */ (
+  await jiti.import('./src/env')
+);
+const { posthogScriptAliases } =
+  /** @type {typeof import('./src/lib/posthog-scripts')} */ (
+    await jiti.import('./src/lib/posthog-scripts')
+  );
 
 /** @type {import("next").NextConfig} */
-const config = withPlausibleProxy({
-  customDomain: process.env.NEXT_PUBLIC_PLAUSIBLE_URL,
-})({
+const baseConfig = {
   output: 'standalone',
   images: {
     remotePatterns: [
@@ -23,11 +27,54 @@ const config = withPlausibleProxy({
     serverActions: {
       bodySizeLimit: '10mb',
     },
+    // Resolves `import { Button } from '@gib/ui'` to the button module alone,
+    // so marketing pages never pull in admin-only Radix widgets or Recharts.
+    // radix-ui is the umbrella package the shadcn components import from.
+    // lucide-react, date-fns and @tabler/icons-react are on Next's default list.
+    optimizePackageImports: ['@gib/ui', 'radix-ui'],
   },
   /** Enables hot reloading for local packages without a build step */
   transpilePackages: ['@gib/backend', '@gib/ui'],
   typescript: { ignoreBuildErrors: true },
-});
+  // PostHog's capture paths end in a slash (/e/, /i/v0/e/), and Next's
+  // built-in trailing-slash redirect would answer those proxied POSTs with a
+  // redirect. It is turned off here and replaced by the redirect below, which
+  // strips trailing slashes everywhere except /ingest.
+  skipTrailingSlashRedirect: true,
+  redirects: async () => [
+    {
+      source: '/:path((?!ingest(?:/|$)).+)/',
+      destination: '/:path',
+      permanent: true,
+    },
+  ],
+  // Same-origin proxy for PostHog, so blocklists that match the PostHog host
+  // never see the request. The aliased extension scripts (blocked by file
+  // name, see src/lib/posthog-scripts.ts) map back to their real files first.
+  rewrites: async () => {
+    const host = env.NEXT_PUBLIC_POSTHOG_HOST;
+    if (!host) return [];
+    return [
+      ...Object.entries(posthogScriptAliases).map(([name, alias]) => ({
+        source: `/ingest/static/${alias}.js`,
+        destination: `${host}/static/${name}.js`,
+      })),
+      { source: '/ingest/:path*', destination: `${host}/:path*` },
+    ];
+  },
+};
+
+// Serves Plausible's per-site script from this origin so ad blockers see a
+// first-party request. next-plausible 4 takes the full script URL. Its default
+// event path is /api/event, which sits inside Payload's /api routes, so both
+// paths move under /pa.
+const config = env.NEXT_PUBLIC_PLAUSIBLE_SRC
+  ? withPlausibleProxy({
+      src: env.NEXT_PUBLIC_PLAUSIBLE_SRC,
+      scriptPath: '/pa/script.js',
+      apiPath: '/pa/event',
+    })(baseConfig)
+  : baseConfig;
 
 const sentryConfig = {
   // For all available options, see: