docs: restructure documentation with enhanced README

Major documentation reorganization:

1. Renamed dev.md to README.md as the main project README
   - Added professional header with badges and overview
   - Added comprehensive features list with emojis
   - Added quick start sections for both users and developers
   - Added detailed tech stack breakdown
   - Added table of contents for easy navigation
   - Added Contributing section with workflow guidelines
   - Added Testing section with examples
   - Added Building section for all platforms
   - Added License, Acknowledgments, Contact sections
   - Added Roadmap for future versions

2. Moved old README.md to docs/user-manual.md
   - Preserves complete user manual content
   - Now accessible as dedicated user documentation

3. Updated all documentation cross-references
   - installation-guide.md: Updated dev.md references to README
   - user-manual.md: Updated dev.md references to README
   - manual.html: Updated dev.md references to README

The new README provides a professional landing page with:
- Clear project description and features
- Easy navigation for both users and developers
- Comprehensive development documentation
- Contributing guidelines with conventional commits
- Complete testing and building instructions
- Professional badges and formatting

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

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

Author: KevenWMarkham