refactor(fe): replace TanStack Query with SWR + UI/data cleanup

Rombak data layer frontend:
- Hapus @tanstack/react-query (package.json, lockfile, provider di
  dashboard layout) — ganti SWR 2.4.2 + SWRConfig (revalidateOnFocus
  false, deduping 10s, no retry on 404)
- Semua hooks data ditulis ulang ke useSWR; useAction() helper baru
  pengganti useMutation dengan surface kompatibel (mutate/mutateAsync/
  isPending/error)
- useMessages + useMessagesHasMore share satu SWR key — probe cursor
  yang tadinya dobel fetch API sekarang deduped
- WS sync (messages/media/recordings) pindah dari queryClient ke
  SWR mutate dengan filter key + revalidate:false
- useMessageSearch() dipakai search-panel & search-overlay; search
  overlay backdrop div -> button (fix a11y lint)

Rapikan UI + isi data:
- Tab stats recordings: placeholder 'coming soon' diganti stat asli
  (total, ukuran, speaker unik, top speakers)
- Empty states konsisten via EmptyState (images/review/recordings),
  EmptyState terima className
- biome check --write: 0 error, 8 warning pre-existing
- Verifikasi: tsc --noEmit PASS, next build PASS (11 halaman static),
  API live dicek — semua endpoint dashboard/messages/guilds/config/
  voice/media/recordings/review balikin data

services/frontend/src/components/dashboard/channels-section.tsx

@@ -20,7 +20,7 @@ export function ChannelsSection({ guildId }: { guildId?: string }) {
     data: channels = [],
     isLoading,
     error,
-    refetch,
+    mutate: refetch,
   } = useChannels(guildId ?? "", search);
   const { data: detail } = useChannelDetail(selectedId);
 
@@ -124,7 +124,9 @@ export function ChannelsSection({ guildId }: { guildId?: string }) {
                     className="rounded-lg border border-border/40 bg-card/40 px-3 py-2"
                   >
                     <p className="text-xs leading-relaxed text-text-secondary line-clamp-2">
-                      {msg.username}: {renderMessageContent(msg.content, msg.metadata) || "(no text content)"}
+                      {msg.username}:{" "}
+                      {renderMessageContent(msg.content, msg.metadata) ||
+                        "(no text content)"}
                     </p>
                     <p className="mt-1 text-[10px] font-mono text-text-secondary/40">
                       {new Date(msg.created_at).toLocaleString()}