Refactor spawn handling into dedicated event listener

- Moved player spawn logic from join event to a new `PlayerSpawnEvent`.
- Improved separation of concerns by restructuring `VoidWorld` spawning logic.
- Added join logging for better debugging.

src/main/java/eu/mhsl/craftattack/worldmuseum/Main.java

@@ -76,7 +76,14 @@ public class Main {
             final VoidWorld voidWorld = new VoidWorld();
 
             event.setSpawningInstance(voidWorld);
-            MinecraftServer.getSchedulerManager().scheduleNextTick(() -> {
+            System.out.println("[Join] Player " + player.getUsername() +" joined the server.");
+        });
+
+        globalEventHandler.addListener(PlayerSpawnEvent.class, event -> {
+            if(!event.isFirstSpawn()) return;
+            MuseumPlayer player = (MuseumPlayer) event.getPlayer();
+            final VoidWorld voidWorld = new VoidWorld();
+
             player.setPermissionLevel(4);
             player.setRespawnPoint(voidWorld.getSpawn());
             player.setGameMode(GameMode.SPECTATOR);
@@ -85,9 +92,6 @@ public class Main {
             voidWorld.movePlayer(player);
         });
 
-            System.out.println("[Join] Player " + player.getUsername() +" joined the server.");
-        });
-
         try {
             PORT = Integer.parseInt(args[0]);
         } catch (Exception e) {