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-moderation.ts

@@ -1,20 +1,35 @@
 import useSWR from "swr";
 import { moderationApi } from "@/lib/api";
-import type { ModerationStats } from "@/lib/types";
+import type { ModerationAction, ModerationStats } from "@/lib/types";
 
-export function useModerationStats() {
-  return useSWR<ModerationStats>(["moderation-stats"], () =>
-    moderationApi.getStats(),
+export function useModerationStats(initialData?: ModerationStats) {
+  return useSWR<ModerationStats>(
+    ["moderation-stats"],
+    () => moderationApi.getStats(),
+    { fallbackData: initialData },
   );
 }
 
-export function useModerationActions(status?: string, actionType?: string) {
+export function useModerationActions(
+  status?: string,
+  actionType?: string,
+  initialData?: ModerationAction[],
+) {
+  const key = [
+    "moderation-actions",
+    status ?? "__all__",
+    actionType ?? "__all__",
+  ];
   return useSWR(
-    ["moderation-actions", status ?? "__all__", actionType ?? "__all__"],
+    key,
     async () => {
       const res = await moderationApi.listActions(100, status, actionType);
       return res.data;
     },
-    { keepPreviousData: true },
+    {
+      keepPreviousData: true,
+      fallbackData:
+        !status && !actionType && initialData ? initialData : undefined,
+    },
   );
 }