feat(ad): 提现看视频广告后端支持(withdrawal_ad 场景 + 开关下发)

- pangle-callback 新增 withdrawal_ad 场景:不发金币、只记一条幂等(coin=0),
  避免提现看视频被穿山甲 S2S 回调误发金币
- ad_config 新增 withdrawal_ad_enabled 开关(默认 true),贯穿 admin schema 与
  platform 下发接口,客户端拉取后用(关=直接放行提现)
- 提现广告 eCPM 复用 /ad/ecpm-report,以 ad_type=withdrawal_video 区分收益,无需 DB 迁移

app/admin/schemas/ad_config.py

@@ -15,6 +15,7 @@ class AdConfigOut(BaseModel):
     reward_enabled: bool
     compare_ad_enabled: bool
     coupon_ad_enabled: bool
+    withdrawal_ad_enabled: bool
 
 
 class AdConfigUpdate(BaseModel):
@@ -28,3 +29,4 @@ class AdConfigUpdate(BaseModel):
     reward_enabled: bool | None = None
     compare_ad_enabled: bool | None = None
     coupon_ad_enabled: bool | None = None
+    withdrawal_ad_enabled: bool | None = None