refactor: separate standalone and managed room configs

- veins → shunts rename
- add cfg/standalone/ and cfg/<room>/ structure
- remove old data/*.json (moved to cfg/<room>/data/)
- update build.py and ctrl scripts

artery/shunts/mercadopago/core/config.py

@@ -0,0 +1,30 @@
+"""Configuration for MercadoPago mock vein."""
+
+from pathlib import Path
+from pydantic_settings import BaseSettings
+
+ENV_FILE = Path(__file__).parent.parent / ".env"
+
+
+class MercadoPagoMockConfig(BaseSettings):
+    """Configuration for MercadoPago (MOCK) vein."""
+
+    api_port: int = 8006
+    mock_data_path: str = "./mock_data"
+
+    # Mock behavior
+    enable_random_delays: bool = True
+    min_delay_ms: int = 200
+    max_delay_ms: int = 800
+    error_rate: float = 0.0  # 0.0 to 1.0
+
+    # Default payment status
+    default_payment_status: str = "approved"  # approved, pending, rejected
+
+    model_config = {
+        "env_file": ENV_FILE if ENV_FILE.exists() else None,
+        "env_file_encoding": "utf-8",
+    }
+
+
+settings = MercadoPagoMockConfig()