refactor: move backend in apps/backend

apps/backend/app/Observers/EventObserver.php

@@ -0,0 +1,25 @@
+<?php
+
+namespace apps\backend\app\Observers;
+
+use apps\backend\app\Models\Event;
+use apps\backend\app\Services\TypesenseService;
+use function App\Observers\app;
+
+class EventObserver
+{
+    public function created(Event $event)
+    {
+        app(TypesenseService::class)->upsertEvent($event);
+    }
+
+    public function updated(Event $event)
+    {
+        app(TypesenseService::class)->upsertEvent($event);
+    }
+
+    public function deleted(Event $event)
+    {
+        app(TypesenseService::class)->deleteEvent($event->id);
+    }
+}