订阅计划

1. GET  /api/v1/subscription/checkin/challenge → 获取签到挑战
2. 前端完成阿里云验证码 → 获得 captcha_verify_param
3. 前端用 challenge 数据计算 HMAC-SHA256 签名
4. POST /api/v1/subscription/checkin → 提交签到

{
  "code": 0,
  "data": {
    "quota_awarded": 200,
    "streak_days": 3,
    "free_quota_remaining": 450
  }
}

curl -X POST https://api.end.shallow.ink/api/v1/subscription/redemption/redeem \
  -H "Authorization: Bearer eyJhbGciOi..." \
  -H "Content-Type: application/json" \
  -d '{"code": "ENDFIELD2026", "cap_token": "cap_xxx"}'