fix: guard PostHog init behind production check

Only initialize PostHog in production to avoid noise and
unnecessary tracking during development.

instrumentation-client.ts

@@ -1,27 +1,28 @@
 import posthog from "posthog-js";
 
-posthog.init(process.env.NEXT_PUBLIC_POSTHOG_PROJECT_TOKEN!, {
-  api_host: "/i",
-  ui_host: "https://us.posthog.com",
-  defaults: "2026-01-30",
-  capture_exceptions: true,
-  debug: process.env.ENVIRONMENT === "development",
+if (process.env.NODE_ENV === "production")
+  posthog.init(process.env.NEXT_PUBLIC_POSTHOG_PROJECT_TOKEN!, {
+    api_host: "/i",
+    ui_host: "https://us.posthog.com",
+    defaults: "2026-01-30",
+    capture_exceptions: true,
+    debug: process.env.ENVIRONMENT === "development",
 
-  before_send: (event) => {
-    if (event?.event === "$exception") {
-      const exceptionList = event.properties.$exception_list || [];
-      const exception = exceptionList[0];
-      if (exception) {
-        if (
-          exception.$exception_source?.includes("posthog") ||
-          exception.value?.includes("posthog") ||
-          exception.value?.includes("__ph_opt_in_out") ||
-          exception.value === "NEXT_REDIRECT"
-        ) {
-          return null;
+    before_send: (event) => {
+      if (event?.event === "$exception") {
+        const exceptionList = event.properties.$exception_list || [];
+        const exception = exceptionList[0];
+        if (exception) {
+          if (
+            exception.$exception_source?.includes("posthog") ||
+            exception.value?.includes("posthog") ||
+            exception.value?.includes("__ph_opt_in_out") ||
+            exception.value === "NEXT_REDIRECT"
+          ) {
+            return null;
+          }
         }
       }
-    }
-    return event;
-  },
-});
+      return event;
+    },
+  });