swarm-ui: a schedules page, one card per scheduled prompt

/schedules lists the controller's scheduled prompts as cards: name as the
title, the agents it fires for, the message, its cadence and next fire.
Edit turns a card into its own form; pause, resume and remove act in place,
and + schedule opens an empty form. The form sends only what changed, so a
rename never moves the fire times, and warns when the start or the repeat
does. Filters reuse the shared card filter bar.

Adds a TextAreaField to the ui kit, and an upcoming mode on RelativeTime so
a next-fire time reads "in 5m". Needs the controller's /api/schedules
routes.

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

@@ -49,6 +49,7 @@ const NAV_ITEMS: { href: string; label: string; accent: string }[] = [
   { href: "/", label: "hives", accent: "var(--purple)" },
   { href: "/agents", label: "agents", accent: "var(--green)" },
   { href: "/jobs", label: "jobs", accent: "var(--pink)" },
+  { href: "/schedules", label: "schedules", accent: "var(--cyan)" },
   { href: "/issues", label: "issues", accent: "var(--yellow)" },
   { href: "/components", label: "components", accent: "var(--blue)" },
 ];