Codex/vietnamese UI ci fixes

[khanhdeptraivaicachuong]

No description provided.

[BigPizzaV3]

Thanks for the contribution. I don't think this PR is ready to merge in its current form.

The main issue is that it does more than add Vietnamese UI support: several existing default strings and install names are changed globally, so Chinese/English users would also see Vietnamese or renamed entries.

Please adjust the PR to keep it scoped to Vietnamese i18n:

• Do not hard-code Vietnamese strings in assets/inject/renderer-inject.js. The injected Codex++ menu should keep the existing language behavior, or localization should be driven by the selected language setting.
• Do not replace source/default UI text directly, e.g. apps/codex-plus-manager/src/model-windows.ts currently returns a Vietnamese error message for every user.
• Remove generated/backup files that should not be committed, especially apps/codex-plus-manager/src/i18n.ts.bak.
• Avoid changing installer/app/shortcut names from Codex++ 管理工具 to Codex++ Manager in this PR. If that change is needed for packaging or CI, it should be a separate PR with its own rationale.
• Please make sure CI/checks run successfully after the cleanup.

A good shape for this PR would be: add i18n-vi.ts, extend the language selector to include Vietnamese, and keep all existing Chinese/English/default behavior unchanged unless the selected language is Vietnamese.

[BigPizzaV3]

Codex++ maintainer review note

当前 main 下这个 PR 仍存在 merge conflict，暂时不能合并。请先 rebase 到最新 main 并解决冲突；更新后我们会重新跑针对性测试再复审。

This PR currently conflicts with main, so it is not mergeable yet. Please rebase onto the latest main and resolve the conflicts, then we can review and test it again.