React: Restructure documentation with step-based flow

Improves React integration documentation with a clearer step-by-step approach:
- Enhanced installation instructions with clearer package manager options
- Added comprehensive error handling for React 19+ and earlier versions
- Expanded configuration examples with detailed feature explanations
- Improved structured logging examples and best practices
- Enhanced session replay configuration with security considerations
- Added custom tracing examples with meaningful attributes
- Better organized next steps and additional resources

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <[email protected]>

Author: codyde