feat(cps): 微信网页授权接入——落地页拿 openid/昵称头像,用户级群统计

- 服务号网页授权(WX_MP_APPID/SECRET,区别于 App 的 WECHAT_APP_ID):
  落地页 base 静默拿 openid;点「领券」补 userinfo 拿昵称头像(交互触发避快照页)
- 新表 cps_wx_user + cps_click 加 openid + 迁移;integrations/wx_oauth
- /c/{code} 授权链路 + 回调 /wx/oauth/cb + cookie 免重复授权;click 带 openid
- admin 群详情加「群内微信用户」(领券画像)端点
- 下单归因到人需 user-level sid,本期只做身份+领券侧

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

app/models/__init__.py

@@ -10,6 +10,7 @@ from app.models.cps_activity import CpsActivity  # noqa: F401
 from app.models.cps_group import CpsGroup  # noqa: F401
 from app.models.cps_link import CpsClick, CpsLink  # noqa: F401
 from app.models.cps_order import CpsOrder  # noqa: F401
+from app.models.cps_wx_user import CpsWxUser  # noqa: F401
 from app.models.comparison_milestone import ComparisonMilestoneClaim  # noqa: F401
 from app.models.coupon_state import (  # noqa: F401
     CouponClaimRecord,