Add a way to open Coder Desktop when it's not visible in the menu bar

Currently if a user's menu bar is full of other apps, causing Coder Desktop to be hidden, then there is no way to open Coder Desktop without first closing other apps until it shows up.

Bellow are some potential ways to solve the problem:

**Open Coder Desktop's tray menu on focus**

I'm not sure if this is possible but if it is it would be a nice workaround to the issue. This was also the behavior I was hoping was already working when I ran into this issue.

**Open a standalone window**

There seems to be two ways to implement this behavior:

1. Make Coder Desktop a "real" app rather than a background app.
This solves the problem but causes Coder Desktop to always be in the dock even when no windows are open which could be seen as annoying.

2. Ship two apps, one background one "real".
This is probably the best solution in terms of UX but with having to build and maintain two separate apps in one.

ファイルやテストは指定されていません。まず、Coder Desktop が macOS のメニューバーアプリまたはバックグラウンドアプリとしてどのように構成されているかを調べ、提案されている focus、standalone-window、dual-app のアプローチを比較してください。メニューバー項目が非表示の場合でもユーザーが Coder Desktop を開けるようになり、その結果の dock の動作が選択した UX と一致すれば完了です。

索引モデルが issue の本文から書いたものです。