Add Notification Backend Protocol (#24)

Reviewed-on: #24

src/va_agent/config.py

@@ -31,6 +31,7 @@ class AgentSettings(BaseSettings):
         "artifacts/bnt-orquestador-cognitivo-dev/notifications"
     )
     notifications_max_to_notify: int = 5
+    notifications_window_hours: float = 48
 
     # MCP configuration
     mcp_audience: str