feat: add auto-select from preferences and type picker

- Add MediaTypeAsk (0) as the default, mapping old video_audio to Ask
- Show Video/Audio/Ask type picker when no default media type is set
- Auto-select matching format and skip picker when defaults are configured
- Add autoSelectVideoFormat / autoSelectAudioFormat helpers with closest-match
- Add buildFilteredFormatList for type-filtered format lists
- Add Media Type setting in settings UI (Ask/Video/Audio)
- Add --merge-output-format mp4 for video downloads via yt-dlp
- Fix formatLabelForDisplay to show Height fallback and Extension
- Add cookies volume mount to docker-compose.yml
- Document cookies setup and new features in README

docker-compose.yml

@@ -15,6 +15,7 @@ services:
       - TZ=${TZ}
     volumes:
       - uptodown_data:/data
+      - ./cookies.txt:/cookies.txt:ro # Optional: cookies file for yt-dlp auth
 
 volumes:
   uptodown_data: