fix(ui): design-system consistency — typography, borders, admin IA, search removal

- typography: font-semibold/font-medium → font-bold throughout (card, dialog, empty-state, notification-bell, quiz-experience, questions-panel, profile-manage)
- borders: border → border-2 for content containers (leaderboard error, notifications page, quiz pass screen, quiz option tiles, learning-panel error)
- admin IA: remove Card-in-SectionPanel nesting from announce-panel, challenges-panel, physical-orders-panel; SectionPanel gains optional actions slot
- announce-panel: flat composer + live preview; history as flat list; cancel-edit button
- lockout: raw textarea → Textarea design-system component
- global-search: delete component and all references (feature removed)
- progress.tsx: dir="ltr" for correct RTL fill direction; remove rtl:me-auto

frontend/src/app/notifications/page.tsx

@@ -48,7 +48,7 @@ export default function NotificationsPage() {
           <Skeleton className="h-8 w-44" />
           <Skeleton className="h-4 w-72" />
         </div>
-        <div className="rounded-2xl border border-border/70 bg-card p-6 shadow-soft">
+        <div className="rounded-2xl border-2 border-border/70 bg-card p-6 shadow-soft">
           <div className="flex items-center gap-3">
             <Skeleton className="h-10 w-10 rounded-xl" />
             <div className="flex-1 space-y-1.5">