计费

submit gen     reserve  (held += cost,  available -= cost,  credits unchanged)
   │
   ├── success → charge   (credits -= cost, held -= cost,  transactions row written)
   │
   └── failure → release  (held -= cost,  credits unchanged, no transactions row)

GET https://vibetoken.cn/api/v1/billing/balance

{
  "credits": 42.50,
  "held": 1.20,
  "available": 41.30,
  "currency": "CNY"
}

POST https://vibetoken.cn/api/v1/billing/coupons/redeem

{
  "credited": 5.0,
  "currency": "CNY",
  "balance": 42.50
}

GET https://vibetoken.cn/api/v1/billing/transactions

{
  "data": [
    {
      "id": "txn_01HXYZ",
      "credits": -0.05,
      "amount": 0.05,
      "payment_method": "usage",
      "status": "completed",
      "created_at": "2025-01-15T11:00:00Z"
    }
  ],
  "total": 150,
  "page": 1,
  "per_page": 20
}

POST https://vibetoken.cn/api/v1/billing/alerts

DELETE https://vibetoken.cn/api/v1/billing/alerts/{id}