feat: implement global SFXManager singleton and integrate into main scene initialization

scenes/main.gd

@@ -720,8 +720,12 @@ func _auto_start_from_lobby():
 
 func _start_game():
 	if multiplayer.is_server():
+		# Delay spawn assignment to allow clients to finish instantiating Player nodes
+		# via MultiplayerSpawner. If called too early, the RPC is dropped and clients
+		# are left misplaced at the default starting position.
+		await get_tree().create_timer(1.0).timeout
+		
 		# NOW assign spawn positions for EVERYONE (Host, Client, Bots)
-		# We do this BEFORE the stabilization delay so players are moved away from (0,0) immediately.
 		_assign_random_spawn_positions()
 
 		# Wait for Nakama websocket to actually be open, up to 5 seconds
@@ -735,9 +739,9 @@ func _start_game():
 					wait_time += 0.2
 				
 		# Stabilization delay to allow clients to finish loading and spawning
-		# We wait 1.5s to ensure the 1.2s loading screen buffer has finished
+		# We wait 0.5s to ensure the remainder of the 1.2s loading screen buffer has finished
 		# before the countdown starts.
-		await get_tree().create_timer(1.5).timeout
+		await get_tree().create_timer(0.5).timeout
 		
 		# PRE-GAME COUNTDOWN (3s)
 		# Spawn static obstacles before countdown starts (Stop n Go only)