docs: enhance README with modern layout and comprehensive information

[TenSoja]

📝 Summary

This PR completely revamps the README.md to provide a more professional, comprehensive, and engaging documentation that better represents pgModeler's 19 years of excellence and technical sophistication.

🚀 Key Improvements

Visual & Layout

• ✅ Added modern badge layout with key project metrics
• ✅ Professional centered header with clear value proposition
• ✅ Organized content in logical, scannable sections
• ✅ Improved readability with emojis and consistent formatting

Content Enhancements

• ✅ Technical Excellence Section: Highlights 96.5% C++ codebase and modern C++17 features
• ✅ Performance Achievements: ~80% improvement metrics from v1.1.0
• ✅ Engineering Highlights: Modular architecture, plugin system, schema microlanguage
• ✅ Creator Spotlight: Recognition of Raphael Araújo e Silva's work and vision
• ✅ Project Legacy: 19-year journey from pgsqlDBM to pgModeler

Information Updates

• ✅ Updated requirements: Qt 6.4+ (dropped 6.2/6.3 support)
• ✅ PostgreSQL 17 support
• ✅ Corrected project timeline (2006-2025 = 19 years)
• ✅ Fixed download metrics (custom badge vs GitHub's 0 downloads)

User Experience

• ✅ Eliminated redundant information between badges and text
• ✅ Added collapsible "Known Issues" section
• ✅ Clear call-to-action sections for donations and contributions
• ✅ Better Quick Start guide with visual steps

🎯 Why This Matters

pgModeler is an incredible project that deserves documentation that matches its quality. This README now:

• Celebrates the technical excellence of the 96.5% C++ codebase
• Honors 19 years of continuous development
• Showcases the creator's passion and expertise
• Provides clear value proposition for new users
• Encourages community contribution more effectively

📊 Before vs After

Before: Basic text-heavy layout with duplicated info and outdated metrics
After: Professional, comprehensive documentation worthy of this amazing project

✅ Checklist

• All information verified against official sources
• No breaking changes to existing links or structure
• Improved readability and visual appeal
• Eliminated redundancies and duplications
• Updated technical requirements and support info
• Enhanced call-to-action sections

This update transforms the README into a document that truly represents pgModeler's status as the premier PostgreSQL database modeler! 🐘✨