fix(api): 修正用户列表查询逻辑以避免重复

- 将查询语句从 activity 表改为 user 表，优化数据来源
- 修改排序字段由 user_id 改为 id，保持一致性
- 移除代码中对用户 ID 的去重逻辑，简化处理流程
- 保持空用户名用用户 ID 字符串替代的逻辑不变

server/internal/api/ymt_users.go

@@ -32,9 +32,9 @@ func (a *YMTUsersAPI) list(w http.ResponseWriter, r *http.Request) {
 			limit = n
 		}
 	}
-	sql1 := "SELECT DISTINCT user_id, COALESCE(user_name, '') AS name FROM activity WHERE user_id IS NOT NULL"
+	sql1 := "SELECT id, name FROM user WHERE id IS NOT NULL"
 	args := []interface{}{}
-	sql1 += " ORDER BY user_id ASC LIMIT ?"
+	sql1 += " ORDER BY id ASC LIMIT ?"
 	args = append(args, limit)
 	rows, err := a.ymt.Query(sql1, args...)
 	if err != nil {
@@ -54,12 +54,6 @@ func (a *YMTUsersAPI) list(w http.ResponseWriter, r *http.Request) {
 		if !id.Valid {
 			continue
 		}
-		if _, ok := used[id.Int64]; ok {
-			// 根据 ID 去重
-			continue
-		}
-		used[id.Int64] = struct{}{}
-
 		n := strings.TrimSpace(name.String)
 		if n == "" {
 			n = strconv.FormatInt(id.Int64, 10)