refactor(repository): 收敛 model/repository 分层为唯一持久化入口

将 OpenFlare 与平台业务的数据访问从 model 与 apps 直连迁入 repository，
model 仅保留实体与无 IO 规则；补充 code-check 架构守卫与开发规范。

internal/repository/upload_stat.go

@@ -5,6 +5,10 @@ package repository
 
 import (
 	"context"
+	"time"
+
+	"gorm.io/gorm"
+	"gorm.io/gorm/clause"
 
 	db "github.com/Rain-kl/Wavelet/internal/infra/persistence"
 	"github.com/Rain-kl/Wavelet/internal/model"
@@ -18,3 +22,76 @@ func ListUploadStats(ctx context.Context) ([]model.UploadStat, error) {
 	}
 	return stats, nil
 }
+
+// GetTotalUploadStat returns the aggregate total-dimension stats row.
+func GetTotalUploadStat(ctx context.Context) (model.UploadStat, error) {
+	var total model.UploadStat
+	if err := db.DB(ctx).
+		Where("dimension = ? AND stat_key = ?", model.UploadStatDimensionTotal, "").
+		First(&total).Error; err != nil {
+		return model.UploadStat{}, err
+	}
+	return total, nil
+}
+
+// ListUploadStatsByDimension returns stats rows for a single dimension.
+func ListUploadStatsByDimension(ctx context.Context, dimension string) ([]model.UploadStat, error) {
+	var rows []model.UploadStat
+	if err := db.DB(ctx).Where("dimension = ?", dimension).Find(&rows).Error; err != nil {
+		return nil, err
+	}
+	return rows, nil
+}
+
+// DeleteAllUploadStatsTx removes every row from w_upload_stats within a transaction.
+func DeleteAllUploadStatsTx(tx *gorm.DB) error {
+	return tx.Where("1 = 1").Delete(&model.UploadStat{}).Error
+}
+
+// UpsertUploadStatDeltaTx applies an incremental count/size delta for one dimension key.
+func UpsertUploadStatDeltaTx(tx *gorm.DB, dimension, key string, countDelta, sizeDelta int64) error {
+	return tx.Clauses(clause.OnConflict{
+		Columns: []clause.Column{
+			{Name: "dimension"},
+			{Name: "stat_key"},
+		},
+		DoUpdates: clause.Assignments(map[string]any{
+			"file_count": gorm.Expr(
+				"CASE WHEN w_upload_stats.file_count + ? < 0 THEN 0 ELSE w_upload_stats.file_count + ? END",
+				countDelta,
+				countDelta,
+			),
+			"file_size": gorm.Expr(
+				"CASE WHEN w_upload_stats.file_size + ? < 0 THEN 0 ELSE w_upload_stats.file_size + ? END",
+				sizeDelta,
+				sizeDelta,
+			),
+			"updated_at": time.Now(),
+		}),
+	}).Create(&model.UploadStat{
+		Dimension: dimension,
+		StatKey:   key,
+		FileCount: countDelta,
+		FileSize:  sizeDelta,
+	}).Error
+}
+
+// RebuildUploadStats clears w_upload_stats and re-applies deltas for every active upload
+// inside a single transaction. applyDelta should apply +1 stats for one upload row.
+func RebuildUploadStats(ctx context.Context, applyDelta func(tx *gorm.DB, upload *model.Upload) error) error {
+	return db.DB(ctx).Transaction(func(tx *gorm.DB) error {
+		if err := DeleteAllUploadStatsTx(tx); err != nil {
+			return err
+		}
+		uploads, err := ListActiveUploadsTx(tx)
+		if err != nil {
+			return err
+		}
+		for i := range uploads {
+			if err := applyDelta(tx, &uploads[i]); err != nil {
+				return err
+			}
+		}
+		return nil
+	})
+}