feat: the rebuild gamemode of "Gauntlet"

scripts/managers/gacha_manager.gd

@@ -37,18 +37,14 @@ func pull(banner_id: String, count: int) -> Array:
 		"count": count
 	})
 	
-	var result = await NakamaManager.client.rpc_async(
-		NakamaManager.session,
-		"perform_gacha_pull",
-		payload
-	)
+	var result = await BackendService.perform_gacha_pull(banner_id, count)
 	
-	if result.is_exception():
-		var msg = result.get_exception().message
+	if result.get("success", false) == false:
+		var msg = str(result.get("error", "Unknown error"))
 		push_error("[GachaManager] Gacha pull failed: " + msg)
 		return []
 		
-	var parsed = JSON.parse_string(result.payload)
+	var parsed = result.get("data", {})
 	if typeof(parsed) != TYPE_DICTIONARY or not parsed.has("results"):
 		return []