selfbot streaming: verified live; capture via system ffmpeg x11grab

End-to-end verified with a real burner token + voice channel: login OK, posts
to the text channel, joins voice, and Go-Live streams the host :1 desktop.

- selfbot.ts now captures the X display with the SYSTEM ffmpeg (reliable
  x11grab) and pipes it into prepareStream, instead of relying on the lib's
  bundled libav input devices (not portable). Capture process is killed on stop.
- package.json: trustedDependencies (node-av, @lng2004/node-datachannel) so the
  native streaming deps build automatically on bun install (incl. Docker).
- Dropped the unused nvenc path (the lib's exported `nvenc` is undefined at
  runtime); software H264 encode for now.

bot/bun.lock

@@ -24,6 +24,10 @@
       },
     },
   },
+  "trustedDependencies": [
+    "@lng2004/node-datachannel",
+    "node-av",
+  ],
   "packages": {
     "@babel/runtime": ["@babel/runtime@7.29.7", "", {}, "sha512-Nq8OhGWiZIZGV6hLHoyAKLLcJihP/xFeBMGJoUrxTX2psI8dCifzLhZISFb+VWS3wFMRDmCGw5R+dOySCqPLhw=="],