feat: PKGBUILD 打包

[JohnChiao75]

• fix: 将 mediakit 依赖编译到程序中
• fix: CI 系统库污染产物 → 删除后 media_kit_libs_linux 自动接管捆绑
• feat: 打包 AUR 包

Checklist / 检查清单

• I have read and understood the contribution guidelines. / 我已阅读并理解贡献指南。

• I have signed the CLA. / 我已签署 CLA。

Description / 描述

• This is a breaking change. / 这是一个重大更改。

• This change requires a server-side update. / 此更改需要服务器端更新。

• This change is compatible with the current version of TouchFish Client. / 此更改与当前版本的 TouchFish Client 兼容。

• This change causes a behavior change that may affect existing users. / 此更改会导致行为更改，可能会影响现有用户。

[ILoveScratch2]

删除依赖并不能迫使 Flutter 静态打包：

Run flutter build linux --release
Building Linux application...                                   
CMake Error at flutter/ephemeral/.plugin_symlinks/media_kit_video/linux/CMakeLists.txt:53 (target_link_libraries):
  Target "media_kit_video_plugin" links to:

    PkgConfig::mpv

  but the target was not found.  Possible reasons include:

    * There is a typo in the target name.
    * A find_package call is missing for an IMPORTED target.
    * An ALIAS target is missing.



CMake Generate step failed.  Build files cannot be regenerated correctly.
Unable to generate build files
Error: Process completed with exit code 1.