重构通道管理逻辑，支持通过任务删除不同类型通道；引入 Asynq 处理异步任务；更新数据库结构以支持通道类型区分

web/tasks/channel.go

@@ -0,0 +1,18 @@
+package tasks
+
+import (
+	"encoding/json"
+	"github.com/hibiken/asynq"
+	"log/slog"
+)
+
+const RemoveChannel = "channel:remove"
+
+func NewRemoveChannel(ids []int32) *asynq.Task {
+	bytes, err := json.Marshal(ids)
+	if err != nil {
+		slog.Error("序列化删除通道任务失败", "error", err)
+		return nil
+	}
+	return asynq.NewTask(RemoveChannel, bytes)
+}