feat: add PostHog utility functions for user identification

- Create centralized identifyUserInPostHog function
- Add resetPostHogIdentity function for logout handling
- Implement comprehensive person properties mapping
- Follow PostHog best practices for user identification
- Centralize PostHog logic to avoid code duplication

web/src/lib/posthog-utils.ts

@@ -0,0 +1,45 @@
+import { pb } from "./pb"
+
+/**
+ * Identifies a user in PostHog with their PocketBase user data
+ * Follows PostHog best practices for user identification
+ * 
+ * @param posthog - PostHog instance
+ * @param user - PocketBase user model (optional, will use current auth if not provided)
+ */
+export function identifyUserInPostHog(posthog: any, user?: any) {
+	if (!posthog) return
+	
+	const userData = user || pb.authStore.model
+	
+	if (!userData) return
+	
+	// Use PocketBase user ID as distinct_id (unique string)
+	// Pass all available person properties for complete profile
+	posthog.identify(userData.id, {
+		email: userData.email,
+		username: userData.username,
+		name: userData.username, // Use username as name if no separate name field
+		created: userData.created,
+		updated: userData.updated,
+		admin: userData.admin || false,
+		avatar: userData.avatar || null,
+		// Add any other relevant user properties
+		user_id: userData.id,
+		email_verified: userData.emailVisibility || false,
+	})
+}
+
+/**
+ * Resets PostHog identity (should be called on logout)
+ * This unlinks future events from the user
+ * 
+ * @param posthog - PostHog instance
+ */
+export function resetPostHogIdentity(posthog: any) {
+	if (!posthog) return
+	
+	// Reset PostHog identity to unlink future events from this user
+	// This is important for shared computers and follows PostHog best practices
+	posthog.reset()
+}