Refactor audio and video processing logic; add audio file handling

- Commented out the application menu setting in Electron main process.
- Modified the audio export IPC handler to streamline audio parameter handling.
- Enhanced the video processing logic to accommodate audio-only mode.
- Updated the parameters parsing to differentiate between audio and video files.
- Added a speaker icon for audio files in the file thumbnails component.
- Adjusted the sidebar component to handle both audio and video files.
- Updated various components to respect the audio-only mode, disabling certain controls.
- Introduced a new `onlyAudio` flag in parameters to manage audio-specific settings.
- Added new dependencies for react-icons to support the speaker icon.
- Created a temporary script for testing FFmpeg commands.