Landing dashboard for the current user

Aggregates the landing dashboard for the authenticated caller in one read. Authorization: any authenticated organization member — organization administrators see the whole organization; every other caller sees only what lies inside the spaces they hold space:read on. Returns summary (pendingApprovals, runsInProgress, doneToday counts), pendingApprovals (up to 20 playbook runs awaiting approval, newest first), activity (the latest 30 activity events, newest first — type is an open string), and recentSpaces (up to 6 non-archived spaces, most recently updated first). doneToday counts completed activity since UTC midnight.