Show unique participants instead of total registrations in hero section

Update HeroSection component to display the count of unique participants based on email addresses rather than the sum of all attendees across sessions.

Replit-Commit-Author: Agent
Replit-Commit-Session-Id: 9b278ad5-3a45-420e-ba83-0847baf9924f
Replit-Commit-Checkpoint-Type: full_checkpoint
Replit-Commit-Event-Id: dce0d821-7558-4b75-a1b9-4e7148a340d4
Replit-Commit-Screenshot-Url: https://storage.googleapis.com/screenshot-production-us-central1/04133160-d2cd-42c9-82f0-4e08d800b951/9b278ad5-3a45-420e-ba83-0847baf9924f/szOT2Og
Replit-Helium-Checkpoint-Created: true

Author: marcselman

client/src/components/HeroSection.tsx

@@ -27,10 +27,15 @@ interface HeroSectionProps {
 export function HeroSection({ edition, sessions, userEmail }: HeroSectionProps) {
   const backdropImage = useMemo(() => getRandomBackdrop(), []);
 
-  const totalRegistrations = sessions.reduce(
-    (sum, session) => sum + session.attendees.length,
-    0
-  );
+  const uniqueParticipants = useMemo(() => {
+    const emails = new Set<string>();
+    sessions.forEach(session => {
+      session.attendees.forEach(attendee => {
+        emails.add(attendee.email.toLowerCase());
+      });
+    });
+    return emails.size;
+  }, [sessions]);
 
   const userRegistrations = userEmail
     ? sessions.filter((s) => isEmailInAttendees(userEmail, s.attendees)).length
@@ -99,10 +104,10 @@ export function HeroSection({ edition, sessions, userEmail }: HeroSectionProps)
                   </div>
                   <div className="flex items-center gap-2">
                     <Users className="h-4 w-4" />
-                    <span className="text-2xl font-bold text-white" data-testid="text-registration-count">
-                      {totalRegistrations}
+                    <span className="text-2xl font-bold text-white" data-testid="text-participant-count">
+                      {uniqueParticipants}
                     </span>
-                    <span>inschrijvingen</span>
+                    <span>deelnemer{uniqueParticipants !== 1 ? "s" : ""}</span>
                   </div>
                   {userEmail && userRegistrations > 0 && (
                     <div className="rounded-full bg-white/20 px-3 py-1">