feat(customers): 发送/接收列改今日口径(对齐云客;本地消息表Asia/Shanghai今日聚合)

- CustomerOut 加 send_today/receive_today(路由赋值,非ORM列)
- /api/customers 每页一次 GROUP BY(owner IN 走复合索引前缀)
- 前端列优先今日值,无消息数据回退原raw字段;列名对齐云客「发送条数/接收条数」
- TDD:今日3发2收+昨日不计入+无消息客户0

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

yunke-server/app/api/schemas.py

@@ -25,6 +25,10 @@ class CustomerOut(BaseModel):
     channel: str
     owner_account_id: str | None = None
     friend_nickname: str | None = None
+    # 今日发送/接收条数(本地消息表按 Asia/Shanghai 今日聚合,对齐云客口径;
+    # 非 ORM 列,由路由赋值,2026-08-22)
+    send_today: int | None = None
+    receive_today: int | None = None
     friend_remark: str | None = None
     real_name: str | None = None
     phone: str | None = None