feat: init db demo

[DVKunion]

• [ ] #25 初步完成 B/S 改造
• [ ] #32 基本完成 api 框架信息
• [ ] #34 完成阿里云、sealos sdk对接实现的一件部署
• [ ] #36 初步完成流量统计
• [ ] #38 登录页
• [ ] #40 代理服务页
• [ ] #42 系统配置页

[DVKunion]

I don't think you can use sqlite to implement the query API first. You should abstract a middle layer to expand other possible database choices.

maybe declare a database.go ?