feat: add balance and ledger endpoints for tenant

- Implemented MyBalance and MyLedgerPage methods in the ledger service to retrieve current user balance and transaction history for a specified tenant.
- Added corresponding test cases for MyBalance and MyLedgerPage methods in the ledger test suite.
- Created DTOs for balance response and ledger items to structure the response data.
- Updated Swagger documentation to include new endpoints for retrieving tenant balance and ledgers.
- Added HTTP tests for the new endpoints to ensure proper functionality.

backend/app/http/tenant/dto/me_balance.go

@@ -0,0 +1,19 @@
+package dto
+
+import (
+	"time"
+
+	"quyun/v2/pkg/consts"
+)
+
+// MeBalanceResponse 返回当前用户在当前租户下的余额信息（租户内隔离）。
+type MeBalanceResponse struct {
+	// Currency 币种：当前固定 CNY（金额单位为分）。
+	Currency consts.Currency `json:"currency"`
+	// Balance 可用余额：可用于购买/消费。
+	Balance int64 `json:"balance"`
+	// BalanceFrozen 冻结余额：用于下单冻结/争议期等。
+	BalanceFrozen int64 `json:"balance_frozen"`
+	// UpdatedAt 更新时间：余额变更时更新。
+	UpdatedAt time.Time `json:"updated_at"`
+}