List namespaces

curl --request GET \
  --url https://api.deyta.ai/gateway/v1/namespaces \
  --header 'Authorization: Bearer <token>'

{
  "success": true,
  "data": [
    {
      "id": "ns_abc123",
      "org_id": "org_xyz789",
      "name": "customer-support",
      "mcp_endpoint_url": "https://api.deyta.ai/mcp/ns_abc123",
      "created_at": "2025-01-15T10:30:00.000Z",
      "updated_at": "2025-01-15T10:30:00.000Z",
      "description": "Customer support knowledge base",
      "external_reference_id": "ext_ref_001"
    }
  ],
  "pagination": {
    "page": 1,
    "pageSize": 20,
    "total": 45,
    "totalPages": 3
  }
}