feat: Enhance PostHog integration with referral tracking and error handling

- Added referral code tracking in PostHog initialization to capture initial and last seen referral codes.
- Wrapped PostHog capture calls in a safeCapture function to prevent app breakage due to ad-blockers.
- Introduced PostHogReferral component in PostHogProvider for improved referral tracking.

surfsense_web/components/providers/PostHogProvider.tsx

@@ -5,17 +5,17 @@ import posthog from "posthog-js";
 import type { ReactNode } from "react";
 import "../../instrumentation-client";
 import { PostHogIdentify } from "./PostHogIdentify";
+import { PostHogReferral } from "./PostHogReferral";
 
 interface PostHogProviderProps {
 	children: ReactNode;
 }
 
 export function PostHogProvider({ children }: PostHogProviderProps) {
-	// posthog-js is initialized by importing instrumentation-client.ts above
-	// We wrap the app with the PostHogProvider for hook access
 	return (
 		<PHProvider client={posthog}>
 			<PostHogIdentify />
+			<PostHogReferral />
 			{children}
 		</PHProvider>
 	);