Add tappable toast actions and navigate to status on post success

[Dimillian]

Motivation

• Make toasts actionable so tapping a toast can perform an application action instead of only dismissing it.
• Specifically allow the "post sent" success toast to navigate to the created status detail when tapped.
• Provide an extensible mechanism so other toasts can carry actions in the future.

Description

• Added Toast.Action nested struct and an optional action property to ToastCenter.Toast, and updated the initializer and equality logic to include the action id.
• Updated ToastOverlayView to invoke action.handler() when a toast is tapped before dismissing the toast.
• Wired the post-success toast in StatusEditor.ToolbarItems to set an action that calls routerPath.navigate(to: .statusDetailWithStatus(status: status)) so tapping the success toast opens the status detail.
• Kept existing toast behaviors (show, update, dismiss, progress handling) unchanged apart from the added action support.

Testing

• No automated tests were executed in this environment because XcodeBuildMCP/CI was not available here.
• Please run a full build and package tests locally or in CI (per project guidelines) to validate compilation and behavior.

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Codex Task