feat(frontend): rebuild as SSR with server-authoritative shared state

Rombak total alur data frontend: dari static-export CSR (tiap browser
fetch sendiri + akumulasi state voice per-tab) jadi server-side rendering.

Frontend (Next.js):
- next.config: output export -> standalone; halaman jadi server components
- server data layer baru src/lib/api/server.ts (GMW_BACKEND_URL, no window)
- dashboard/media/messages/moderation/recordings/voice page -> RSC yang
  fetch backend di render-time, seed ke client view (SWR fallbackData)
- hook-hook utama terima initialData -> first paint data server, revalidate
  SWR setelahnya, tanpa spinner-blank-load
- messages: guild/channel/tab/selected dibaca dari URL di server, page awal
  di-fetch server-side

Shared realtime state (voice) server-authoritative:
- backend src/modules/voice/live-speaker.ts: agregat voice_active_user dari
  gateway jadi snapshot authoritatif (single source of truth semua browser)
- GET /api/voice/status kini include activeSpeakers
- WS initial states kirim voice_state snapshot saat connect (late join
  langsung dapat state yang sama, bukan daftar kosong)
- useSpeakers seed dari server snapshot + voice_state full-replace +
  voice_active_user delta upsert

Deploy:
- flake.nix: frontend package build SSR standalone (server.js wrapper,
  GMW_FRONTEND_PORT=4017); proxy nginx template proxy / -> Next server,
  /api + /ws tetap ke backend :4001

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

@@ -24,17 +24,27 @@ type MessagePage = { data: MessageRecord[]; nextCursor: string | null };
  * useMessagesHasMore derive from this one SWR key, so the cursor probe no
  * longer triggers a duplicate API call.
  */
-function useMessagesPage(guildId: string, channelId?: string) {
+function useMessagesPage(
+  guildId: string,
+  channelId?: string,
+  initialPage?: MessagePage,
+) {
   const key = guildId ? msgKeys.list(guildId, channelId) : null;
-  return useSWR<MessagePage>(key, () =>
-    messagesApi.list(guildId, 50, channelId || undefined),
+  return useSWR<MessagePage>(
+    key,
+    () => messagesApi.list(guildId, 50, channelId || undefined),
+    { fallbackData: initialPage },
   );
 }
 
 // ── Messages list (paginated, cursor-based) ──────
 
-export function useMessages(guildId: string, channelId?: string) {
-  const page = useMessagesPage(guildId, channelId);
+export function useMessages(
+  guildId: string,
+  channelId?: string,
+  initialPage?: MessagePage,
+) {
+  const page = useMessagesPage(guildId, channelId, initialPage);
   return {
     ...page,
     data: page.data?.data,