fix: install Node.js and use web client for YouTube n-challenge solving

- ios player client doesn't support cookies, switch to web
- Node.js is required for yt-dlp to solve YouTube's n-challenge;
  without it only image formats are served

app/downloader.py

@@ -47,7 +47,7 @@ async def extract_audio(url: str) -> Path:
         "--audio-format", "mp3",
         "--audio-quality", "128K",
         "--format", "bestaudio/best/b",
-        "--extractor-args", "youtube:player_client=ios,web",
+        "--extractor-args", "youtube:player_client=web",
         "--output", outtmpl,
     ]