List all vaults

{
  "vaults": [
    {
      "id": "vault_abc123",
      "name": "Contract Repository",
      "description": "Secure storage for client contracts",
      "enableGraph": true,
      "totalObjects": 1247,
      "totalBytes": 2847362048,
      "createdAt": "2024-01-01T00:00:00Z"
    }
  ],
  "total": 1
}