feat: implement withdrawal improvements P01-P05

- P04: fix Withdrawal.TableName() to return 'withdrawals'
- P03: add WithdrawalStatus* and WithdrawalMethod* constants; replace magic numbers; add CommissionTypeWithdrawCancel=338
- P01: add POST /v1/public/user/withdrawal_cancel to cancel pending withdrawals with ownership check, row lock, commission refund, and audit log
- P02: add method/account/qr_code_url fields to Withdrawal model and API; add input validation (qr_code_url required for Alipay/Wechat, account required for bank)
- P05: add method filter to admin GET /v1/admin/user/withdrawal/list

Co-authored-by: multica-agent <github@multica.ai>

internal/logic/admin/user/getWithdrawalListLogic.go

@@ -42,6 +42,9 @@ func (l *GetWithdrawalListLogic) GetWithdrawalList(req *types.GetWithdrawalListR
 	if req.Status != nil {
 		query = query.Where("status = ?", *req.Status)
 	}
+	if req.Method != nil {
+		query = query.Where("method = ?", *req.Method)
+	}
 
 	var total int64
 	if err := query.Count(&total).Error; err != nil {
@@ -62,6 +65,9 @@ func (l *GetWithdrawalListLogic) GetWithdrawalList(req *types.GetWithdrawalListR
 			Content:   row.Content,
 			Status:    row.Status,
 			Reason:    row.Reason,
+			Method:    row.Method,
+			Account:   row.Account,
+			QrCodeUrl: row.QrCodeUrl,
 			CreatedAt: row.CreatedAt.UnixMilli(),
 			UpdatedAt: row.UpdatedAt.UnixMilli(),
 		})

internal/logic/admin/user/withdrawalCommon.go

@@ -37,9 +37,9 @@ func approveWithdrawal(ctx context.Context, svcCtx *svc.ServiceContext, withdraw
 		}
 
 		if err := tx.Model(&usermodel.Withdrawal{}).
-			Where("id = ? AND status = 0", withdrawalID).
+			Where("id = ? AND status = ?", withdrawalID, usermodel.WithdrawalStatusPending).
 			Updates(map[string]interface{}{
-				"status": 1,
+				"status": usermodel.WithdrawalStatusApproved,
 				"reason": "",
 			}).Error; err != nil {
 			return errors.Wrapf(xerr.NewErrCode(xerr.DatabaseUpdateError), "approve withdrawal failed: %v", err)
@@ -80,9 +80,9 @@ func rejectWithdrawal(ctx context.Context, svcCtx *svc.ServiceContext, withdrawa
 		// Commission was NOT deducted at application time under the new logic,
 		// so rejection requires no refund — only a status update.
 		return tx.Model(&usermodel.Withdrawal{}).
-			Where("id = ? AND status = 0", withdrawalID).
+			Where("id = ? AND status = ?", withdrawalID, usermodel.WithdrawalStatusPending).
 			Updates(map[string]interface{}{
-				"status": 2,
+				"status": usermodel.WithdrawalStatusRejected,
 				"reason": reason,
 			}).Error
 	})