feat: Update documentation structure and content

- Added a link to the Recent Improvements section in the README.md for better visibility of new features.
- Removed the SEARCH_FILTER_FIX.md file as its content has been integrated into other documentation.
- Deleted the consolidate_docs.py script as its functionality is no longer needed after the documentation consolidation.
- Removed the outdated CHANGELOG.md file and replaced it with a new structure that consolidates all changelog information.
- Created a new DOCUMENTATION_INDEX.md file to provide a comprehensive guide to the documentation structure.
- Updated the docs/README.md to reflect the new documentation organization and included links to preserved legacy documentation.

docs/DOCUMENTATION_INDEX.md

@@ -0,0 +1,78 @@
+# TheChart Documentation Index
+
+## 📚 Complete Documentation Guide
+
+### 🚀 Quick Navigation
+
+#### Essential Documents
+- **[README.md](../README.md)** - Project overview and quick start guide
+- **[USER_GUIDE.md](../USER_GUIDE.md)** - Complete user manual with features and shortcuts
+- **[DEVELOPER_GUIDE.md](../DEVELOPER_GUIDE.md)** - Development setup, testing, and architecture
+- **[API_REFERENCE.md](../API_REFERENCE.md)** - Technical documentation and system APIs
+
+#### Project History
+- **[CHANGELOG.md](../CHANGELOG.md)** - Version history and release notes
+- **[IMPROVEMENTS_SUMMARY.md](../IMPROVEMENTS_SUMMARY.md)** - Recent enhancements and new features
+
+### 📖 Documentation Organization
+
+This project uses a **consolidated documentation structure** to avoid redundancy and improve maintainability:
+
+#### Root Level Documents (Primary)
+All main documentation is located in the project root for easy access:
+
+- **README.md** - Entry point for all users
+- **USER_GUIDE.md** - Comprehensive user documentation
+- **DEVELOPER_GUIDE.md** - Complete development guide
+- **API_REFERENCE.md** - Technical reference documentation
+- **CHANGELOG.md** - Version history
+- **IMPROVEMENTS_SUMMARY.md** - Latest feature summary
+
+#### docs/ Folder (Reference)
+The docs/ folder contains:
+- Legacy documentation files (preserved for reference)
+- Specialized topic documentation
+- This documentation index
+
+### 🔍 Find What You Need
+
+#### New Users
+Start with: **[USER_GUIDE.md](../USER_GUIDE.md)**
+- Application features
+- Getting started guide
+- Keyboard shortcuts
+- UI customization
+
+#### Developers
+Start with: **[DEVELOPER_GUIDE.md](../DEVELOPER_GUIDE.md)**
+- Environment setup
+- Testing procedures
+- Architecture overview
+- Contributing guidelines
+
+#### System Administrators
+Check: **[API_REFERENCE.md](../API_REFERENCE.md)**
+- Export system details
+- Configuration options
+- Technical specifications
+- Integration information
+
+### 🏗️ Documentation Standards
+
+All documentation follows these principles:
+- **Single Source of Truth**: No duplicate content across files
+- **Clear Navigation**: Easy cross-references and linking
+- **Up-to-date**: Regular updates with code changes
+- **User-focused**: Organized by user needs, not technical structure
+
+### 📝 Contributing to Documentation
+
+When updating documentation:
+1. Edit the appropriate root-level file
+2. Update cross-references if needed
+3. Test all links for accuracy
+4. Follow the established format and style
+
+---
+
+*Last updated: August 6, 2025*