Allow event registration when status is 'in_progress' (not just 'published')

Events that have started (in_progress) should still accept registrations until
registration_closes_at. Previously only 'published' status allowed registration.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

app/Domain/Event/Models/Event.php

@@ -111,7 +111,7 @@ public function scopeRegistrationOpen($query)
 
     public function isRegistrationOpen(): bool
     {
-        if ($this->status !== EventStatus::Published) {
+        if (!in_array($this->status, [EventStatus::Published, EventStatus::InProgress])) {
             return false;
         }