Improved security and performance

Implemented a content security policy and strengthened input validation.
Improved the visual distinction between the current month and adjacent months.
Enhanced day cell sizing and streamlined the week number display.

UI enhacements and new features added (monthly and yearly calender)

Enhancements:-

UI Improvements: Updated the CSS for a modern look, including:
Changed background color for better contrast.
Increased font size for improved readability.
Enhanced box shadow for a more elevated appearance.
Added hover effects on the body and clock icon for better interactivity.
Increased icon size for improved visibility.