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/app/(dashboard)/media/view.tsx

@@ -0,0 +1,19 @@
+"use client";
+
+import { MusicPlayer } from "@/components/media/music-player";
+import type { MediaState } from "@/lib/types";
+import { useWebSocket } from "@/lib/ws/context";
+
+export default function MediaView({
+  initialStatus,
+}: {
+  initialStatus?: MediaState;
+}) {
+  const ws = useWebSocket();
+
+  return (
+    <div className="space-y-5 animate-fade-in-up">
+      <MusicPlayer ws={ws} initialData={initialStatus} />
+    </div>
+  );
+}