feat: add TenantLedger model and query generation

- Introduced TenantLedger model with fields for managing tenant transactions, including ID, TenantID, UserID, OrderID, transaction Type, Amount, and balance details.
- Implemented CRUD operations for TenantLedger with methods for Create, Update, Delete, and Reload.
- Generated query methods for TenantLedger to facilitate database interactions, including filtering, pagination, and aggregation functions.
- Established relationships with Order model for foreign key references.

backend/database/models/media_assets.query.gen.go

@@ -47,18 +47,18 @@ type mediaAssetQuery struct {
 	mediaAssetQueryDo mediaAssetQueryDo
 
 	ALL       field.Asterisk
-	ID        field.Int64
-	TenantID  field.Int64
-	UserID    field.Int64
-	Type      field.Field
-	Status    field.Field
-	Provider  field.String
-	Bucket    field.String
-	ObjectKey field.String
-	Meta      field.JSONB
-	DeletedAt field.Field
-	CreatedAt field.Time
-	UpdatedAt field.Time
+	ID        field.Int64  // 主键ID：自增；仅用于内部关联
+	TenantID  field.Int64  // 租户ID：多租户隔离关键字段；所有查询/写入必须限定 tenant_id
+	UserID    field.Int64  // 用户ID：资源上传者；用于审计与权限控制
+	Type      field.Field  // 资源类型：video/audio/image；决定后续处理流程（转码/缩略图/封面等）
+	Status    field.Field  // 处理状态：uploaded/processing/ready/failed/deleted；ready 才可被内容引用对外提供
+	Provider  field.String // 存储提供方：例如 s3/minio/oss；便于多存储扩展
+	Bucket    field.String // 存储桶：对象所在 bucket；与 provider 组合确定存储定位
+	ObjectKey field.String // 对象键：对象在 bucket 内的 key；不得暴露可长期复用的直链（通过签名URL/token下发）
+	Meta      field.JSONB  // 元数据：JSON；包含 hash、duration、width、height、bitrate、codec 等；用于展示与计费/风控
+	DeletedAt field.Field  // 软删除时间：非空表示已删除；对外接口需过滤
+	CreatedAt field.Time   // 创建时间：默认 now()；用于审计与排序
+	UpdatedAt field.Time   // 更新时间：默认 now()；更新状态/元数据时写入
 
 	fieldMap map[string]field.Expr
 }