feat(dashboard): expose trust reputation + reactions leaderboard

- GET /api/dashboard/reactions: top reacted messages (net add-remove),
  joined with message content, channel name, top 3 emoji breakdown
- Users tab: colored trust tier badge (Trusted/Netral/At Risk/Kritis)
  in list rows + detail panel (was plain number badge)
- Dashboard: new Reactions sub-tab with leaderboard
  (rank, emoji cluster, message, author, channel, count)

services/frontend/src/hooks/index.ts

@@ -4,6 +4,7 @@ export {
   useChannelDetail,
   useChannels,
   useStats,
+  useTopReactions,
   useUserDetail,
   useUsers,
 } from "./use-dashboard";

services/frontend/src/hooks/use-dashboard.ts

@@ -6,6 +6,7 @@ import type {
   DashboardChannelDetail,
   DashboardStats,
   DashboardUserDetail,
+  TopReactedMessage,
 } from "@/lib/types";
 
 export function useStats() {
@@ -63,3 +64,9 @@ export function useChannelDetail(channelId: string | null) {
     () => dashboardApi.getChannelDetail(channelId!),
   );
 }
+
+export function useTopReactions(limit = 20) {
+  return useSWR<TopReactedMessage[]>(["dashboard-reactions", limit], () =>
+    dashboardApi.getTopReactions(limit),
+  );
+}