docs(readme): reorganize structure and enhance professional tone

- Restructured document with clear sections (Quick Start, Command Reference, etc.)
- Updated installation URL to use shorter shelltime.xyz/i endpoint
- Removed casual language and emojis for professional tone
- Added comprehensive table format for performance metrics
- Enhanced security documentation with technical details
- Organized commands into logical categories
- Added new Troubleshooting and Resources sections
- Improved formatting consistency throughout
- Removed redundant API documentation link

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Co-Authored-By: Claude <noreply@anthropic.com>

Author: AnnatarHe