Add theme management and settings functionality

- Introduced `ThemeManager` to handle application themes using `ttkthemes`.
- Added `SettingsWindow` for user preferences including theme selection and UI settings.
- Integrated theme selection into the main application with a menu for quick access.
- Enhanced UI components with custom styles based on the selected theme.
- Implemented tooltips for better user guidance across various UI elements.
- Updated dependencies to include `ttkthemes` for improved visual appeal.

docs/DOCUMENTATION_SUMMARY.md

@@ -0,0 +1,109 @@
+# Documentation Consolidation Summary
+
+## Overview
+This document summarizes the documentation consolidation and updates performed to improve the TheChart project documentation structure.
+
+## Changes Made
+
+### 1. Documentation Structure Consolidation
+- **Removed**: `docs/UI_IMPROVEMENTS.md` (redundant file)
+- **Consolidated**: UI/UX improvements documentation into `docs/FEATURES.md`
+- **Enhanced**: Main `README.md` with recent updates section
+- **Updated**: `docs/README.md` (documentation index) with comprehensive navigation
+
+### 2. Content Integration
+
+#### FEATURES.md Enhancements
+- **Added**: Modern UI/UX System section (new in v1.9.5)
+- **Added**: Professional Theme Engine documentation
+- **Added**: Comprehensive Keyboard Shortcuts section
+- **Added**: Settings and Theme Management documentation
+- **Added**: Smart Tooltip System documentation
+- **Added**: Enhanced Technical Architecture section
+- **Added**: UI/UX Technical Implementation section
+
+#### CHANGELOG.md Updates
+- **Added**: Version 1.9.5 with comprehensive UI/UX overhaul documentation
+- **Added**: Settings and Configuration System section
+- **Added**: Enhanced User Experience section
+- **Added**: Technical Architecture Improvements section
+
+#### README.md Improvements
+- **Updated**: Title and description to emphasize modern UI/UX
+- **Added**: Recent Major Updates section highlighting v1.9.5 improvements
+- **Added**: Quick start guidance for new users
+- **Updated**: Documentation links with better descriptions
+- **Added**: Documentation navigation guide reference
+
+### 3. Cross-Reference Updates
+- **Updated**: All internal links to reflect consolidated structure
+- **Enhanced**: Documentation index with comprehensive navigation
+- **Added**: Task-based navigation in docs/README.md
+- **Improved**: User type-based documentation guidance
+
+## Current Documentation Structure
+
+```
+docs/
+├── README.md              # Documentation index and navigation guide
+├── FEATURES.md            # Complete feature documentation (includes UI/UX)
+├── KEYBOARD_SHORTCUTS.md  # Comprehensive shortcut reference
+├── EXPORT_SYSTEM.md       # Data export functionality
+├── DEVELOPMENT.md         # Development setup and testing
+├── CHANGELOG.md           # Version history and improvements
+└── DOCUMENTATION_SUMMARY.md # This summary (new)
+
+README.md                  # Main project README with quick start
+```
+
+## Documentation Highlights
+
+### For End Users
+1. **Modern UI/UX**: Complete documentation of the new theme system
+2. **Keyboard Efficiency**: Comprehensive shortcut system documentation
+3. **Feature Guidance**: Consolidated feature documentation with examples
+4. **Quick Navigation**: Task-based and user-type-based navigation
+
+### For Developers
+1. **Technical Architecture**: Enhanced architecture documentation
+2. **UI/UX Implementation**: Technical details of theme system
+3. **Code Organization**: Clear separation of concerns documentation
+4. **Development Workflow**: Comprehensive development guide
+
+## Quality Improvements
+
+### Content Quality
+- **Comprehensive Coverage**: All major features and improvements documented
+- **Clear Structure**: Hierarchical organization with clear headings
+- **Practical Examples**: Code snippets and usage examples maintained
+- **Cross-References**: Better linking between related sections
+
+### User Experience
+- **Progressive Disclosure**: Information organized by user expertise level
+- **Task-Oriented**: Documentation organized around user tasks
+- **Quick Access**: Multiple entry points and navigation paths
+- **Searchable**: Clear headings and consistent formatting
+
+### Maintenance
+- **Reduced Redundancy**: Eliminated duplicate information
+- **Single Source of Truth**: Consolidated information reduces maintenance burden
+- **Version Alignment**: Documentation synchronized with current codebase
+- **Future-Proof**: Structure supports easy updates and additions
+
+## Next Steps
+
+### Recommended Maintenance
+1. **Keep Features Updated**: Update FEATURES.md as new UI/UX improvements are added
+2. **Maintain Changelog**: Continue detailed changelog entries for version tracking
+3. **Review Navigation**: Periodically review docs/README.md navigation for completeness
+4. **User Feedback**: Collect user feedback on documentation effectiveness
+
+### Future Enhancements
+1. **Screenshots**: Consider adding screenshots of the new UI themes
+2. **Video Guides**: Potential for video demonstrations of key features
+3. **API Documentation**: If public APIs develop, consider separate API docs
+4. **Internationalization**: Structure supports future translation efforts
+
+---
+
+**Documentation consolidation completed**: All major UI/UX improvements are now properly documented and easily discoverable through the improved navigation structure.