feat: 实现账本服务和仓库层，提供账本的创建、查询、更新、删除和恢复功能。

internal/repository/ledger_repository.go

@@ -111,6 +111,14 @@ func (r *LedgerRepository) GetDefault(userID uint) (*models.Ledger, error) {
 	return &ledger, nil
 }
 
+// UnsetAllDefaults unsets the default status for all ledgers of a user
+func (r *LedgerRepository) UnsetAllDefaults(userID uint) error {
+	if err := r.db.Model(&models.Ledger{}).Where("user_id = ? AND is_default = ?", userID, true).Update("is_default", false).Error; err != nil {
+		return fmt.Errorf("failed to unset default ledgers: %w", err)
+	}
+	return nil
+}
+
 // SetDefault sets a ledger as the default ledger
 func (r *LedgerRepository) SetDefault(userID uint, id uint) error {
 	// Start a transaction

internal/service/ledger_service.go

@@ -83,7 +83,7 @@ func (s *LedgerService) CreateLedger(userID uint, input LedgerInput) (*models.Le
 
 	// If this is set as default, we need to unset other defaults
 	if input.IsDefault {
-		if err := s.repo.SetDefault(userID, 0); err != nil {
+		if err := s.repo.UnsetAllDefaults(userID); err != nil {
 			return nil, fmt.Errorf("failed to unset default ledgers: %w", err)
 		}
 	}