The onboarding tour tells users they can right-click a folder to pause its
background work, but only the per-worker buttons in the BackgroundTasks bar
existed. Add a 'Pause/Resume background work' context-menu item that toggles
all four workers (thumbnail/metadata/embedding/tagging) for the folder.
To keep the bar and the menu in sync, worker-pause state moves from
BackgroundTasks' local state into the store (the canonical owner of app
state), so pausing from either surface reflects in both. Reuses the existing
set_worker_paused / get_worker_states commands; no backend change.
LyAhn
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