Added new screenshots for Custom Option and Download Settings. Updated audio_format, main, and playlist screenshots. Removed obsolete subtitle_options screenshot.
Updated README.md to reference local screenshot files instead of external URLs. Renamed 'audio-only.png' to 'audio_format.png' and 'subtitles.png' to 'subtitle_options.png' for consistency with README references.
Added new screenshots for audio-only, main interface, playlist, and subtitles to the branding assets. These images can be used for documentation or promotional purposes.
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