Remove Helper Apps (Menu Helper, Login Helper)

Start by tracing the main app, Login Helper, and Menu Helper entry points and how login-item launches and server shutdown currently work. Check the activation-policy transitions described in the issue and verify that normal launches, login launches, window closing, quitting, and logout preserve the stated behavior without either helper app.

Currently, Postgres.app has two helper apps:

• Login Helper (starts PostgreSQL servers on login, and the menu helper)
• Menu Helper (shows the menu bar icon)

The main reason for the helpers is that we don't want to show any user interface on login (dock icon, app window) but still launch servers.

However, I've realised that we could maybe do away with the helpers alltogether by dynamically changing the "activation policy" using NSApp.setActivationPolicy(.regular) and NSApp.setActivationPolicy(.accessory) to show/hide the dock icon.

Then instead of a helper app, we could just launch the main app on login.

• if the app is opened as a login item, we call .setActivationPolicy(.accessory)
• if the app is opened normally (eg. double clicking in Finder) we call .setActivationPolicy(.regular)
• if the main window is closed we call .setActivationPolicy(.accessory)
• when the app is terminated (eg. using the "quit" command or when the user logs out) we stop all servers and quit the app

Behavior would be similar to how it is now, but we would only have a single app and no helpers.

Advantages:

• app shows up as a normal login item
• sparkle check happens every login (doesn't require explicitly launching main app)
• no more version conflicts (eg. when a different version of main app vs helper is running)
• no more apple script errors when controlling main app from menu helper (it's the same process)
• servers quit automatically on logout #834
• Prevent macOS Tahoe warning #817