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/contents.gen.go

@@ -18,19 +18,19 @@ const TableNameContent = "contents"
 
 // Content mapped from table <contents>
 type Content 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"`
-	Title               string                   `gorm:"column:title;type:character varying(255);not null" json:"title"`
-	Description         string                   `gorm:"column:description;type:text;not null" json:"description"`
-	Status              consts.ContentStatus     `gorm:"column:status;type:character varying(32);not null;default:draft" json:"status"`
-	Visibility          consts.ContentVisibility `gorm:"column:visibility;type:character varying(32);not null;default:tenant_only" json:"visibility"`
-	PreviewSeconds      int32                    `gorm:"column:preview_seconds;type:integer;not null;default:60" json:"preview_seconds"`
-	PreviewDownloadable bool                     `gorm:"column:preview_downloadable;type:boolean;not null" json:"preview_downloadable"`
-	PublishedAt         time.Time                `gorm:"column:published_at;type:timestamp with time zone" json:"published_at"`
-	DeletedAt           gorm.DeletedAt           `gorm:"column:deleted_at;type:timestamp with time zone" json:"deleted_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；用于内容引用" json:"id"`                                                                      // 主键ID：自增；用于内容引用
+	TenantID            int64                    `gorm:"column:tenant_id;type:bigint;not null;comment:租户ID：多租户隔离关键字段；所有查询/写入必须限定 tenant_id" json:"tenant_id"`                                                       // 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              int64                    `gorm:"column:user_id;type:bigint;not null;comment:用户ID：内容创建者/发布者；用于权限与审计（例如私有内容仅作者可见）" json:"user_id"`                                                            // 用户ID：内容创建者/发布者；用于权限与审计（例如私有内容仅作者可见）
+	Title               string                   `gorm:"column:title;type:character varying(255);not null;comment:标题：用于列表展示与搜索；建议限制长度（由业务校验）" json:"title"`                                                         // 标题：用于列表展示与搜索；建议限制长度（由业务校验）
+	Description         string                   `gorm:"column:description;type:text;not null;comment:描述：用于详情页展示；可为空字符串" json:"description"`                                                                        // 描述：用于详情页展示；可为空字符串
+	Status              consts.ContentStatus     `gorm:"column:status;type:character varying(32);not null;default:draft;comment:状态：draft/reviewing/published/unpublished/blocked；published 才对外展示" json:"status"`    // 状态：draft/reviewing/published/unpublished/blocked；published 才对外展示
+	Visibility          consts.ContentVisibility `gorm:"column:visibility;type:character varying(32);not null;default:tenant_only;comment:可见性：public/tenant_only/private；仅控制详情可见，正片资源仍需按价格/权益校验" json:"visibility"` // 可见性：public/tenant_only/private；仅控制详情可见，正片资源仍需按价格/权益校验
+	PreviewSeconds      int32                    `gorm:"column:preview_seconds;type:integer;not null;default:60;comment:试看秒数：默认 60；只对 preview 资源生效；必须为正整数" json:"preview_seconds"`                                  // 试看秒数：默认 60；只对 preview 资源生效；必须为正整数
+	PreviewDownloadable bool                     `gorm:"column:preview_downloadable;type:boolean;not null;comment:试看是否允许下载：默认 false；当前策略固定为不允许下载（仅 streaming）" json:"preview_downloadable"`                         // 试看是否允许下载：默认 false；当前策略固定为不允许下载（仅 streaming）
+	PublishedAt         time.Time                `gorm:"column:published_at;type:timestamp with time zone;comment:发布时间：首次发布时写入；用于时间窗与排序" json:"published_at"`                                                       // 发布时间：首次发布时写入；用于时间窗与排序
+	DeletedAt           gorm.DeletedAt           `gorm:"column:deleted_at;type:timestamp with time zone;comment:软删除时间：非空表示已删除；对外接口需过滤" json:"deleted_at"`                                                           // 软删除时间：非空表示已删除；对外接口需过滤
+	CreatedAt           time.Time                `gorm:"column:created_at;type:timestamp with time zone;not null;default:now();comment:创建时间：默认 now()；用于审计与排序" json:"created_at"`                                    // 创建时间：默认 now()；用于审计与排序
+	UpdatedAt           time.Time                `gorm:"column:updated_at;type:timestamp with time zone;not null;default:now();comment:更新时间：默认 now()；编辑内容时写入" json:"updated_at"`                                    // 更新时间：默认 now()；编辑内容时写入
 }
 
 // Quick operations without importing query package