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/app/http/tenant/dto/order.go

@@ -0,0 +1,22 @@
+package dto
+
+import "quyun/v2/database/models"
+
+// PurchaseContentForm defines the request body for purchasing a content using tenant balance.
+type PurchaseContentForm struct {
+	// IdempotencyKey is used to ensure the purchase request is processed at most once.
+	// 建议由客户端生成并保持稳定：同一笔购买重复请求时返回相同结果，避免重复扣款/重复下单。
+	IdempotencyKey string `json:"idempotency_key,omitempty"`
+}
+
+// PurchaseContentResponse returns the order and granted access after a purchase.
+type PurchaseContentResponse struct {
+	// Order is the created or existing order record (may be nil for owner/free-path without order).
+	Order *models.Order `json:"order,omitempty"`
+	// Item is the single order item of this purchase (current implementation is 1 order -> 1 content).
+	Item *models.OrderItem `json:"item,omitempty"`
+	// Access is the content access record after purchase grant.
+	Access *models.ContentAccess `json:"access,omitempty"`
+	// AmountPaid is the final paid amount in cents (CNY 分).
+	AmountPaid int64 `json:"amount_paid,omitempty"`
+}