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/CHANGELOG.md

@@ -5,6 +5,41 @@ All notable changes to TheChart project are documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [1.9.5] - 2025-08-05
+
+### 🎨 Major UI/UX Overhaul
+- **Added**: Professional theme system with ttkthemes integration
+- **Added**: 8 curated themes (Arc, Equilux, Adapta, Yaru, Ubuntu, Plastik, Breeze, Elegance)
+- **Added**: Dynamic theme switching without restart
+- **Added**: Theme persistence between sessions
+- **Added**: Comprehensive settings window with tabbed interface
+- **Added**: Smart tooltip system with context-sensitive help
+- **Improved**: Table selection highlighting and alternating row colors
+- **Improved**: Modern styling for all UI components (buttons, frames, forms)
+- **Improved**: Professional card-style layouts and enhanced spacing
+
+### ⚙️ Settings and Configuration System
+- **Added**: Advanced settings window (accessible via F2)
+- **Added**: Theme selection with live preview
+- **Added**: UI preferences and customization options
+- **Added**: About dialog with detailed application information
+- **Added**: Settings persistence across application restarts
+
+### 💡 Enhanced User Experience
+- **Added**: Intelligent tooltips for all interactive elements
+- **Added**: Specialized help for pathology scales and medicine options
+- **Added**: Non-intrusive tooltip timing (500-800ms delay)
+- **Added**: Quick theme switching via menu bar
+- **Improved**: Visual hierarchy with better typography and spacing
+- **Improved**: Professional color schemes across all themes
+
+### 🏗️ Technical Architecture Improvements
+- **Added**: Modular theme manager with dependency injection
+- **Added**: Tooltip management system
+- **Added**: Enhanced UI manager with theme integration
+- **Improved**: Code organization with separate concerns
+- **Improved**: Error handling with graceful theme fallbacks
+
 ## [1.7.0] - 2025-08-05
 
 ### ⌨️ Keyboard Shortcuts System