Refactor FFmpeg processing and improve IPC communication

- Removed unnecessary path normalization in FFmpegProcessor.
- Updated main process to use electronAPI for IPC calls instead of ipcRenderer directly.
- Enhanced MergeList component to handle string paths instead of File objects.
- Improved OutputPath component to utilize electronAPI for folder dialog and desktop path retrieval.
- Refactored SideBar component to streamline file handling and processing status updates.
- Cleaned up unused utility functions and adjusted parameters handling across components.
- Updated HTML structure in index.html for better compatibility with Vite.