yt-dlp API - POST /api/download with { "url": "...", "quality": "best", "mode": "both", "iosCompatible": true, "proxy": true, "playlist": false }. Omit "mode" or set it to "both" for video+audio, use "audio" for audio-only, or "video" for video-only. Set "playlist": true to download playlists as a zip. POST /api/music with { "url": "https://music.youtube.com/watch?v=..." }. GET /api/history for download history (requires DATABASE_URL).