feat(gateway): restore Discord GoLive screenshare (dulu pernah ada, hilang saat split microservices)

User: 'dulu sharescreen juga bisa'. Terbukti: commit d50ce86 (Mei 2026)
punya src/media/screenShareController.ts + vendor @dank074/discord-video-stream,
hilang saat rombak monolith -> microservices. Interface ScreenShareController
masih ada di mediaTypes.ts tapi implementasinya tidak.

Restore:
- dep @dank074/discord-video-stream@6.0.0 (npm, dibangun untuk
  discord.js-selfbot-v13 — cocok dengan stack gateway)
- mediaSource.getDirectVideoUrl (yt-dlp --get-url bestvideo+bestaudio)
- screenShareController.ts (BARU): Streamer(client) + prepareStream H264
  720p30 + playStream go-live; owner check via discordPlayer
- media.handler: mode:'screen' di media:queue -> screen path; status
  expose activeMode; stop matiin screen
- FE: tombol Screen di MusicPlayer + hook useMediaQueue({url, mode})

Verifikasi: gateway tsc PASS, FE tsc PASS, biome 0 error, next build PASS.
Nix build pending (dep native @lng2004/node-datachannel butuh pnpm rebuild).

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

@@ -24,7 +24,10 @@ function useMediaAction<TArgs>(fn: (args: TArgs) => Promise<MediaState>) {
 }
 
 export function useMediaQueue() {
-  return useMediaAction((url: string) => mediaApi.queue(url, "music"));
+  return useMediaAction(
+    (input: { url: string; mode?: "music" | "screen" }) =>
+      mediaApi.queue(input.url, input.mode ?? "music"),
+  );
 }
 
 export function useMediaSkip() {