Posthog-fixes (#5901)

PostHog is now initialized with persistence: 'memory' so no cookies are
written on first load. Consent is handled in a PostHogConsentSync
component that switches to localStorage+cookie persistence only when the
user accepts, using the official @posthog/react package (cherry-picked
from 14aaf64)

---------

Co-authored-by: James Brunton <james@stirlingpdf.com>

frontend/src/global.d.ts

@@ -26,16 +26,4 @@ declare module 'axios' {
   }
 }
 
-declare module 'posthog-js/react' {
-  import { ReactNode } from 'react';
-  import posthogJs, { PostHogConfig } from 'posthog-js';
-
-  export const PostHogProvider: React.FC<{
-    client?: typeof posthogJs;
-    options?: Partial<PostHogConfig>;
-    apiKey?: string;
-    children?: ReactNode;
-  }>;
-}
-
 export { };

frontend/src/index.tsx

@@ -9,7 +9,7 @@ import { BrowserRouter } from 'react-router-dom';
 import App from '@app/App';
 import '@app/i18n'; // Initialize i18next
 import posthog from 'posthog-js';
-import { PostHogProvider } from 'posthog-js/react';
+import { PostHogProvider } from '@posthog/react';
 import { BASE_PATH } from '@app/constants/app';
 
 posthog.init('phc_VOdeYnlevc2T63m3myFGjeBlRcIusRgmhfx6XL5a1iz', {
@@ -18,18 +18,19 @@ posthog.init('phc_VOdeYnlevc2T63m3myFGjeBlRcIusRgmhfx6XL5a1iz', {
   capture_exceptions: true, // This enables capturing exceptions using Error Tracking, set to false if you don't want this
   debug: false,
   opt_out_capturing_by_default: true, // Opt-out by default, controlled by cookie consent
+  persistence: 'memory', // No cookies/localStorage written until user opts in
   cross_subdomain_cookie: false,
 });
 
-function updatePosthogConsent(){
-  if(typeof(posthog) == "undefined" || !posthog.__loaded) {
-    return;
-  }
+function updatePosthogConsent() {
+  if (!posthog.__loaded) return;
   const optIn = (window.CookieConsent as any)?.acceptedService?.('posthog', 'analytics') || false;
   if (optIn) {
+    posthog.set_config({ persistence: 'localStorage+cookie' });
     posthog.opt_in_capturing();
   } else {
     posthog.opt_out_capturing();
+    posthog.set_config({ persistence: 'memory' });
   }
   console.log("Updated PostHog consent: ", optIn ? "opted in" : "opted out");
 }