feat: enhance superadmin dashboard overview

backend/app/services/super.go

@@ -2059,6 +2059,74 @@ func (s *super) BatchReviewContents(ctx context.Context, operatorID int64, form
 	return nil
 }
 
+func (s *super) ContentStatistics(ctx context.Context, filter *super_dto.SuperContentStatisticsFilter) (*super_dto.SuperContentStatisticsResponse, error) {
+	// 统一统计时间范围与粒度，默认最近 7 天。
+	reportFilter := &super_dto.SuperReportOverviewFilter{}
+	if filter != nil {
+		reportFilter.TenantID = filter.TenantID
+		reportFilter.StartAt = filter.StartAt
+		reportFilter.EndAt = filter.EndAt
+		reportFilter.Granularity = filter.Granularity
+	}
+	rg, err := s.normalizeReportRange(reportFilter)
+	if err != nil {
+		return nil, err
+	}
+
+	tenantID := int64(0)
+	if filter != nil && filter.TenantID != nil {
+		tenantID = *filter.TenantID
+	}
+
+	// 统计内容总量，支持租户维度过滤。
+	tbl, q := models.ContentQuery.QueryContext(ctx)
+	if tenantID > 0 {
+		q = q.Where(tbl.TenantID.Eq(tenantID))
+	}
+	total, err := q.Count()
+	if err != nil {
+		return nil, errorx.ErrDatabaseError.WithCause(err)
+	}
+
+	// 按天聚合新增内容数量，补齐趋势序列。
+	type contentAggRow struct {
+		Day   time.Time `gorm:"column:day"`
+		Count int64     `gorm:"column:count"`
+	}
+	rows := make([]contentAggRow, 0)
+	query := models.ContentQuery.WithContext(ctx).
+		UnderlyingDB().
+		Model(&models.Content{}).
+		Select("date_trunc('day', created_at) as day, count(*) as count").
+		Where("created_at >= ? AND created_at < ?", rg.startDay, rg.endNext)
+	if tenantID > 0 {
+		query = query.Where("tenant_id = ?", tenantID)
+	}
+	if err := query.Group("day").Scan(&rows).Error; err != nil {
+		return nil, errorx.ErrDatabaseError.WithCause(err)
+	}
+
+	trendMap := make(map[string]int64, len(rows))
+	for _, row := range rows {
+		key := row.Day.Format("2006-01-02")
+		trendMap[key] = row.Count
+	}
+
+	trend := make([]super_dto.SuperContentTrendItem, 0)
+	for day := rg.startDay; !day.After(rg.endDay); day = day.AddDate(0, 0, 1) {
+		key := day.Format("2006-01-02")
+		trend = append(trend, super_dto.SuperContentTrendItem{
+			Date:         key,
+			CreatedCount: trendMap[key],
+		})
+	}
+
+	return &super_dto.SuperContentStatisticsResponse{
+		TotalCount: total,
+		Trend:      trend,
+	}, nil
+}
+
 func (s *super) ListOrders(ctx context.Context, filter *super_dto.SuperOrderListFilter) (*requests.Pager, error) {
 	tbl, q := models.OrderQuery.QueryContext(ctx)