feat(gendao): 添加代码生成工具用于自动生成DAO层代码

- 实现了完整的gendao命令行工具功能
- 添加了模板文件用于生成DAO、DO、Entity等代码结构
- 集成了数据库表字段映射和类型转换功能
- 支持分片表模式匹配和自定义配置选项
- 实现了代码清理和格式化功能
- 提供了灵活的表名过滤和前缀处理机制

cmd/gendao/internal/consts/consts.go

@@ -0,0 +1,13 @@
+// Copyright GoFrame gf Author(https://goframe.org). All Rights Reserved.
+//
+// This Source Code Form is subject to the terms of the MIT License.
+// If a copy of the MIT was not distributed with this file,
+// You can obtain one at https://github.com/gogf/gf.
+
+package consts
+
+const (
+	// DoNotEditKey is used in generated files,
+	// which marks the files will be overwritten by CLI tool.
+	DoNotEditKey = `DO NOT EDIT`
+)