feat: mailbox-centric activity view, reduce log noise from empty polling cycles

Agent-Logs-Url: https://github.com/christianlouis/InboxConverge/sessions/1a78a249-127f-4a73-a454-3c6bafbf6e58

Co-authored-by: christianlouis <361235+christianlouis@users.noreply.github.com>

frontend/package-lock.json

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