Every count in one answer: the bell, each category, tasks

Derived on read from one grouped query plus one indexed count. bell.dot is true when only ambient news is unseen (a quiet dot, never a number). tasks is the open, unexpired "Needs you" count (an integer, from the stored tasks), and bell.count already includes it: a client adds nothing of its own. bell.count is open tasks plus unseen critical plus unseen important.