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.gen.go

@@ -17,15 +17,15 @@ const TableNameContentAccess = "content_access"
 
 // ContentAccess mapped from table <content_access>
 type ContentAccess struct {
-	ID        int64                      `gorm:"column:id;type:bigint;primaryKey;autoIncrement:true" json:"id"`
-	TenantID  int64                      `gorm:"column:tenant_id;type:bigint;not null" json:"tenant_id"`
-	UserID    int64                      `gorm:"column:user_id;type:bigint;not null" json:"user_id"`
-	ContentID int64                      `gorm:"column:content_id;type:bigint;not null" json:"content_id"`
-	OrderID   int64                      `gorm:"column:order_id;type:bigint" json:"order_id"`
-	Status    consts.ContentAccessStatus `gorm:"column:status;type:character varying(16);not null;default:active" json:"status"`
-	RevokedAt time.Time                  `gorm:"column:revoked_at;type:timestamp with time zone" json:"revoked_at"`
-	CreatedAt time.Time                  `gorm:"column:created_at;type:timestamp with time zone;not null;default:now()" json:"created_at"`
-	UpdatedAt time.Time                  `gorm:"column:updated_at;type:timestamp with time zone;not null;default:now()" json:"updated_at"`
+	ID        int64                      `gorm:"column:id;type:bigint;primaryKey;autoIncrement:true;comment:主键ID：自增" json:"id"`                                                              // 主键ID：自增
+	TenantID  int64                      `gorm:"column:tenant_id;type:bigint;not null;comment:租户ID：多租户隔离；与内容、用户归属一致" json:"tenant_id"`                                                       // 租户ID：多租户隔离；与内容、用户归属一致
+	UserID    int64                      `gorm:"column:user_id;type:bigint;not null;comment:用户ID：权益所属用户；用于访问校验" json:"user_id"`                                                              // 用户ID：权益所属用户；用于访问校验
+	ContentID int64                      `gorm:"column:content_id;type:bigint;not null;comment:内容ID：权益对应内容；唯一约束 (tenant_id, user_id, content_id)" json:"content_id"`                         // 内容ID：权益对应内容；唯一约束 (tenant_id, user_id, content_id)
+	OrderID   int64                      `gorm:"column:order_id;type:bigint;comment:订单ID：产生该权益的订单；可为空（例如后台补发/迁移）" json:"order_id"`                                                           // 订单ID：产生该权益的订单；可为空（例如后台补发/迁移）
+	Status    consts.ContentAccessStatus `gorm:"column:status;type:character varying(16);not null;default:active;comment:权益状态：active/revoked/expired；revoked 表示立即失效（例如退款/违规）" json:"status"` // 权益状态：active/revoked/expired；revoked 表示立即失效（例如退款/违规）
+	RevokedAt time.Time                  `gorm:"column:revoked_at;type:timestamp with time zone;comment:撤销时间：当 status=revoked 时写入；用于审计与追责" json:"revoked_at"`                                // 撤销时间：当 status=revoked 时写入；用于审计与追责
+	CreatedAt time.Time                  `gorm:"column:created_at;type:timestamp with time zone;not null;default:now();comment:创建时间：默认 now()；用于审计" json:"created_at"`                        // 创建时间：默认 now()；用于审计
+	UpdatedAt time.Time                  `gorm:"column:updated_at;type:timestamp with time zone;not null;default:now();comment:更新时间：默认 now()；更新 status 时写入" json:"updated_at"`               // 更新时间：默认 now()；更新 status 时写入
 }
 
 // Quick operations without importing query package