refactor(gateway): remove screen-share / GoLive feature entirely

Drop the Discord Go Live (screen share) stack across the discord-gateway:
- delete src/goLive/ (19 modules: Streamer, Demuxer, encoders, WebRTC wrapper, native loader, etc.)
- delete native/libdatachannel-min/ N-API binding + flake native build + LD_LIBRARY_PATH wiring
- delete screenShareController.ts and screen-share tests (goLive-port, golive-*, demuxerNut, screenShareInput)
- mediaSource.ts: remove Invidious helpers + downloadScreenInput (YouTube full-file download)
- mediaTypes.ts: drop ScreenShare* types, narrow MediaMode to 'music' and DiscordPlayerOwner to non-screen
- media.handler.ts: remove screen branch, screenController/screenPlayback, voice-disconnect/reconnect accessor
- commandHandler.ts: stop passing getVoiceStatus / setVoiceController into MediaHandler
- media handler now only handles music; music queue/playback/status untouched

Verification: tsc --noEmit clean, biome clean on touched files, no lingering goLive/screenShare refs in BE/FE/gateway.

flake.nix

@@ -11,11 +11,6 @@
       let
         pkgs = import nixpkgs { inherit system; };
 
-        # libdatachannel for the GoLive N-API binding. nixpkgs 0.24.1 is built
-        # against this host's glibc and ships both lib + dev headers, so the
-        # binding links cleanly inside the Nix sandbox (no manual cmake build).
-        libdatachannel = pkgs.libdatachannel;
-
         # Source filter: `path:` literals do NOT respect .gitignore by default,
         # so a dirty local out/ (stale chunks from previous builds) leaks into
         # the sandbox. Filter out build artifacts explicitly.
@@ -73,7 +68,7 @@
         # NOTE: do NOT use `pnpm install --prod` here — it collapses the
         # public-hoist dir (.pnpm/node_modules) that runtime peer resolution
         # relies on (e.g. @lng2004/node-datachannel and @seydx/node-av-linux-x64
-        # are only reachable through it), silently breaking voice/screenshare.
+        # are only reachable through it), silently breaking voice.
         # Instead we keep the full install's symlink layout and only prune
         # orphaned package dirs + broken symlinks.
         # Must run AFTER tsc (typescript is a devDep) and after native builds.
@@ -167,8 +162,7 @@ WRAPPER
             pkgs.pkg-config
             pkgs.openssl
             pkgs.openssl.dev
-            libdatachannel.dev # rtc/rtc.hpp headers for the GoLive binding
-            pkgs.git # libdatachannel FetchContent clones from GitHub
+            pkgs.git # for any FetchContent-based deps during native builds
             pkgs.cacert
           ];
 
@@ -195,24 +189,6 @@ WRAPPER
                 (cd "$pkg" && npm run install 2>&1 || true)
               fi
             done
-            echo "=== Building libdatachannel-min N-API binding ==="
-            # The GoLive screen-share stack uses a minimal N-API binding
-            # (native/libdatachannel-min) over nixpkgs libdatachannel.
-            (
-              cd native/libdatachannel-min
-              # binding.gyp resolves include/lib from env (LDC_INCLUDE = .dev
-              # include root, LDC_LIB = lib output dir, NAPI_INCLUDE =
-              # node-addon-api include root).
-              NAPI_INCLUDE=$(find ../../node_modules/.pnpm -maxdepth 3 \
-                -type d -path "*node_modules/node-addon-api" | head -1)
-              echo "NAPI_INCLUDE=$NAPI_INCLUDE"
-              LDC_INCLUDE=${libdatachannel.dev} LDC_LIB=${libdatachannel.out}/lib/libdatachannel.so.0.24.1 \
-                NAPI_INCLUDE=$NAPI_INCLUDE \
-                npx node-gyp rebuild 2>&1 || true
-              ls -la build/Release/datachannel_min.node 2>/dev/null \
-                && echo "libdatachannel-min binding OK: $(stat -c%s build/Release/datachannel_min.node) bytes" \
-                || echo "WARN: libdatachannel-min binding build FAILED (screen share disabled)"
-            )
             echo "=== Compiling TypeScript ===="
             npx tsc 2>&1
             echo "=== Fixing @/ path aliases to relative paths ==="
@@ -247,22 +223,6 @@ WRAPPER
             mkdir -p $out/lib/gmw-discord-gateway
             cp -r dist node_modules package.json tsconfig.json $out/lib/gmw-discord-gateway/
 
-            # GoLive native binding — loadNative resolves it relative to
-            # dist/goLive/native.js, i.e. <root>/native/libdatachannel-min/
-            # build/Release/datachannel_min.node; libdatachannel .so must sit
-            # next to it and be on LD_LIBRARY_PATH at runtime.
-            mkdir -p $out/lib/gmw-discord-gateway/native/libdatachannel-min/build/Release
-            cp native/libdatachannel-min/build/Release/datachannel_min.node \
-              $out/lib/gmw-discord-gateway/native/libdatachannel-min/build/Release/ 2>/dev/null || true
-            mkdir -p $out/lib/gmw-discord-gateway/native/libdatachannel-min/build/ldc
-            cp -rL native/libdatachannel-min/build/ldc/libdatachannel.so* \
-              $out/lib/gmw-discord-gateway/native/libdatachannel-min/build/ldc/ 2>/dev/null || true
-            # If the binding failed to build, screen share is simply disabled —
-            # the gateway itself must still start.
-            if [ ! -f $out/lib/gmw-discord-gateway/native/libdatachannel-min/build/Release/datachannel_min.node ]; then
-              echo "WARN: datachannel_min.node missing — GoLive screen share disabled in this build"
-            fi
-
             # Also include drizzle migrations if they exist
             cp -r drizzle $out/lib/gmw-discord-gateway/ 2>/dev/null || true
 
@@ -271,7 +231,6 @@ WRAPPER
 #!${pkgs.runtimeShell}
 cd $out/lib/gmw-discord-gateway
 export PATH=${pkgs.ffmpeg-headless}/bin:${pkgs.yt-dlp}/bin:\$PATH
-export LD_LIBRARY_PATH=${libdatachannel.out}/lib:\$LD_LIBRARY_PATH
 exec ${nodejs}/bin/node dist/index.js
 WRAPPER
             chmod +x $out/bin/gmw-discord-gateway