[v2] Add System Tray support

[SomeoneIsWorking]

Wails v2 currently lacks a built-in system tray runtime API. While v3 is moving towards this, many v2 users still need a cross-platform way to add system tray icons and menus.

This issue tracks the addition of:

• runtime.TraySetSystemTray API for Go.
• Platform-specific implementations (Darwin, Windows, Linux).
• Documentation and examples.

[SomeoneIsWorking]

Sorry I know this issue has been opened a million times but this is only created for the PR.

[github-actions]

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[github-actions]

This issue has been automatically closed due to lack of activity.
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