fix(douyu): 补齐拆分后支付轮询常量导入 + 代理三模式断言测试

- douyu_runner_manual/gold: 导入 core 的 DOUYU_PAYMENT_POLL_* 常量
  (之前仅在 douyu_runner.py 单文件内可见, 拆分后到账轮询会 NameError)
- 新增 tests/test_douyu_runner_proxy.py: 静态/API/关闭三模式 + 降级直连 +
  activity_client session 级 proxies, 兑现 8fe9fdf 提交说明中的行为断言

web/backend/services/douyu_runner_gold.py

@@ -10,6 +10,7 @@ from sqlalchemy.orm import Session
 from core.douyu import DouyuActivityClient, FishFinRechargeClient, FishFinRechargeConfig, FishFinRechargeError
 from ..models import Account, DouyuTask
 from .douyu_service import update_account_profile_from_cookie
+from .douyu_runner_core import DOUYU_PAYMENT_POLL_INTERVAL, DOUYU_PAYMENT_POLL_SECONDS
 
 class GoldMixin:
     """鱼翅充值域：扫码充值、供应商直充与到账轮询。"""

web/backend/services/douyu_runner_manual.py

@@ -8,6 +8,7 @@ from sqlalchemy.orm import Session
 from core.douyu import DouyuActivityClient, DouyuActivityError
 from ..models import Account, DouyuTask
 from .douyu_service import account_uid, update_account_profile_from_cookie
+from .douyu_runner_core import DOUYU_PAYMENT_POLL_INTERVAL, DOUYU_PAYMENT_POLL_SECONDS
 
 class ManualMixin:
     """手册域：精英/电竞手册开通支付、积分查询与到账轮询。"""