Documentation: Ubuntu *.deb based install instruction (and other OS specific install instructions)

### Feature summary

Documentation needs explain *.deb, *.rpm install instruction.

### What problem are you trying to solve?

AppImage based installation on Ubuntu is complex.
Issues:
1) Automatic updates, problems with permissions
2) Desktop icon is not GH App
3) At some point it started to be extremely slow and eat 90%+ CPU

### Proposed solution

The *.deb installation have no any of these problems.

It's hard to find which apt source should be used, so instruction would help.

### Workflow impact

_No response_

### Installation context

_No response_

### Additional context

_No response_

首先定位安装文档和现有的 AppImage 说明。添加清晰的 Ubuntu *.deb 指南，包括应使用哪个 apt 源，并在适用的情况下涵盖 *.rpm 或其他特定于操作系统的安装说明；完成的标准是用户能够找到并按照受支持的软件包安装步骤操作。

由索引模型根据 Issue 内容生成。