chore(demo): enhance ui with responsive design and improved aesthetics

Description

Closes #81

Enhanced the overall user experience and visual appeal of the demo application.

Added an icon and metadata to differentiate search results.
Redisgned the buttons.
Implemented a light/dark mode based on system preferences.
Set a maximum width at the body level to ensure content remains consistent and avoids unexpected width changes.
Addressed screen jerking when the scrollbar appears by applying the CSS rule margin-left: calc(100vw - 100%); to the HTML.
Changed the look and feel of the menu to enhance presentation.
Added a fade-in animation when content appears, making transitions smoother.
Removed autofill styling for inputs to provide a cleaner look.
Reduced the size of the version in the title to optimize display on smaller screens.
Removed position: sticky from the search bar (interaction was buggy).

St.^{:grey_question:}	Category	Percentage	Covered / Total
🟢	Statements	98.36%	481/489
🟢	Branches	93.42%	227/243
🟢	Functions	100%	137/137
🟢	Lines	99.15%	464/468