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/content_access.query.gen.go

@@ -44,15 +44,15 @@ type contentAccessQuery struct {
 	contentAccessQueryDo contentAccessQueryDo
 
 	ALL       field.Asterisk
-	ID        field.Int64
-	TenantID  field.Int64
-	UserID    field.Int64
-	ContentID field.Int64
-	OrderID   field.Int64
-	Status    field.Field
-	RevokedAt field.Time
-	CreatedAt field.Time
-	UpdatedAt field.Time
+	ID        field.Int64 // 主键ID：自增
+	TenantID  field.Int64 // 租户ID：多租户隔离；与内容、用户归属一致
+	UserID    field.Int64 // 用户ID：权益所属用户；用于访问校验
+	ContentID field.Int64 // 内容ID：权益对应内容；唯一约束 (tenant_id, user_id, content_id)
+	OrderID   field.Int64 // 订单ID：产生该权益的订单；可为空（例如后台补发/迁移）
+	Status    field.Field // 权益状态：active/revoked/expired；revoked 表示立即失效（例如退款/违规）
+	RevokedAt field.Time  // 撤销时间：当 status=revoked 时写入；用于审计与追责
+	CreatedAt field.Time  // 创建时间：默认 now()；用于审计
+	UpdatedAt field.Time  // 更新时间：默认 now()；更新 status 时写入
 
 	fieldMap map[string]field.Expr
 }