swarm-ui: the schedules are a folded card on the messages tab

The schedules tab is gone from the nav. Its page, unchanged inside, is a card
on /messages under the broadcast card that starts shut and reads nothing until
opened; its add button and refresh picker move into the card's body.
/schedules redirects to /messages. Docs follow.

frontend/packages/swarm-ui/src/shell/Shell.tsx

@@ -53,7 +53,6 @@ const NAV_ITEMS: { href: string; label: string; accent: string }[] = [
   { href: "/agents", label: "agents", accent: "var(--green)" },
   { href: "/alerts", label: "alerts", accent: "var(--red)" },
   { href: "/jobs", label: "jobs", accent: "var(--pink)" },
-  { href: "/schedules", label: "schedules", accent: "var(--cyan)" },
   { href: "/messages", label: "messages", accent: "var(--purple)" },
   { href: "/notifications", label: "notifications", accent: "var(--yellow)" },
   { href: "/issues", label: "issues", accent: "var(--yellow)" },