chore(dal): remove unused Locker model

pkg/dal/models/locker.go is dead code: it is absent from the gorm-gen model
list in pkg/dal/cmd/gen.go, has no generated query, and no migration creates
a lockers table. Locking is handled by pkg/infra/lock instead.

pkg/dal/models/locker.go

@@ -1,31 +0,0 @@
-// Copyright 2023 sigma
-//
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-//     http://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
-
-package models
-
-import (
-	"gorm.io/plugin/soft_delete"
-)
-
-// Locker locker
-type Locker struct {
-	CreatedAt int64                 `gorm:"autoCreateTime:milli"`
-	UpdatedAt int64                 `gorm:"autoUpdateTime:milli"`
-	DeletedAt soft_delete.DeletedAt `gorm:"softDelete:milli"`
-	ID        string                `gorm:"primaryKey;size:36"`
-
-	Key    string
-	Expire int64
-	Value  string
-}