Wallet ledger activity

Return recent entries from the wallet ledger for the authenticated key's account, newest first. Each entry records a wallet mutation (top-up, reservation, commit, refund) with the signed `microsDelta` applied, the resulting `microsBalanceAfter`, and the `source` and `metadata` describing the cause. Keys without an associated account return an empty list.

curl https://api.voxrouter.ai/v1/credits/activity \
  -H "Authorization: Bearer $VOXROUTER_API_KEY"

{
  "rows": [
    {
      "id": "string",
      "kind": "string",
      "microsDelta": 0,
      "microsBalanceAfter": 0,
      "reservationId": "string",
      "source": "string",
      "metadata": null,
      "createdAt": "string"
    }
  ]
}