Enhance Temperature Converter: Add Multi-Unit Support, Real-Time Conversion, and Conversion History

[Shiven04123]

Description:
The current Temperature Converter provides basic functionality but lacks advanced features and a polished interface.
This enhancement aims to improve usability, interactivity, and visual design, making the tool more professional and user-friendly.

Proposed Improvements:

Multi-Unit Conversion
Extend support for Celsius (°C), Fahrenheit (°F), Kelvin (K), and Rankine (°R).
Conversion logic unified via Kelvin for scalability.

Real-Time Conversion Preview
Live updates of conversion results as the user types or changes units.
Enhances interactivity without cluttering conversion history.

History Bug Fix
Prevented excessive history entries on each keystroke.
Only saves conversion when the “Convert” button is clicked.

Persistent Conversion History
Displays recent conversions in a list below the converter.
Stored in localStorage to remain after page reloads.
Includes a Clear History button for managing entries.

Swap Units Feature
A “🔁 Swap” button allows interchanging source and target units instantly.
Auto-updates conversion preview after swap.

Improved UI/UX
Modern card-style layout with rounded corners and soft shadows.
Hover effects for buttons and clear spacing for inputs and history.
Color scheme improved for readability and visual appeal.
Responsive design for desktop and mobile screens.