feat(channel): 对齐 vivid 最新渠道/模型管理设计

渠道管理(对齐 9db9971/9f6eeca/b607a8d/268a8f7/7f8a87e):
- 列表新增「运行中」(Redis 并发槽位实时计数,与调度同源)和「失败数」
  (event_logs 按渠道聚合)两列
- 行内「同步上游模型」恢复弹窗:默认全开、右侧开关、彩点+单行别名,
  底部「同步模型」批量导入;编辑表单去掉获取模型列表按钮(保存已自动
  全量同步);去掉勾选即解绑语义与 unbind-model 端点
- 导入加固:别名与上游同名报错、同批别名复用拒绝、本地类型冲突拒绝、
  单次上限 50

模型管理(对齐 5545195):
- 模型表单/CreateModel 补齐 max_reference_videos/audios 与
  max_ref_video/audio_seconds 透传

产物(对齐 2253e58):
- 下载结果仅信任 image/*/video/* 响应头,text/plain 等乱报一律按魔数
  嗅探定 MIME

Generated with [Devin](https://devin.ai)

Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

backend/internal/repo/event_repo.go

@@ -668,6 +668,29 @@ func (r *EventRepository) SetAccount(ctx context.Context, eventID, accountID, ac
 		Updates(map[string]any{"account_id": accountID, "account_email": accountEmail}).Error
 }
 
+// FailedByAccount counts failed events grouped by account_id (channel id) —
+// the channel list's 失败数 column.
+func (r *EventRepository) FailedByAccount(ctx context.Context) (map[string]int64, error) {
+	type row struct {
+		AccountID string `gorm:"column:account_id"`
+		Count     int64  `gorm:"column:count"`
+	}
+	var rows []row
+	if err := r.db.WithContext(ctx).
+		Model(&model.EventLog{}).
+		Select("account_id, COUNT(*) AS count").
+		Where("status = ? AND account_id <> ''", "failed").
+		Group("account_id").
+		Scan(&rows).Error; err != nil {
+		return nil, err
+	}
+	out := make(map[string]int64, len(rows))
+	for _, item := range rows {
+		out[item.AccountID] = item.Count
+	}
+	return out, nil
+}
+
 // InFlightByAccount counts pending (in-flight) events grouped by account_id, for
 // the accounts view's live "in-flight" column.
 func (r *EventRepository) InFlightByAccount(ctx context.Context) (map[string]int64, error) {