List AI Gateway budgets

{
  "data": [
    {
      "attributes": {
        "capacity_microcents": 100000000,
        "created_at": "2026-08-24T12:00:00Z",
        "created_by": "admin@example.com",
        "current_period_capacity_microcents": 120000000,
        "current_spend_microcents": 25000000,
        "enabled": true,
        "enforcement": "BLOCK",
        "monitor_id": 12345678,
        "name": "Coding agents",
        "selector": [
          {
            "dim": "user_id",
            "per_value": true,
            "values": [
              "11111111-1111-1111-1111-111111111111"
            ]
          }
        ],
        "tags": {
          "model": "gpt-5.2-codex"
        },
        "updated_at": "2026-08-24T12:00:00Z",
        "warning_threshold": 0.9,
        "window_end": "2026-09-01T00:00:00Z",
        "window_policy": "MONTHLY",
        "window_start": "2026-08-01T00:00:00Z"
      },
      "id": "11111111-1111-1111-1111-111111111111",
      "type": "budgets"
    }
  ]
}