ZONE 1: BROWSER UI ZONE 2: FLASK API ZONE 3: BACKGROUND ZONE 4: OUTPUT POST /download GET /status fetch formats start create job check exec metadata clean name save JSON state ready BROWSER_UI API_DOWNLOAD JOB_ID_STORE API_STATUS GET_INFO SPAWN_THREAD YT_DLP_JSON SANITIZE_FILE FFMPEG_MERGE POLL_RESULT DOWNLOADS_FOLDER