Add Dark/Light Mode Toggle Functionality

Description:
The application currently supports only light mode, which may not suit all users’ preferences, especially in low-light environments. Adding a toggle mode feature will allow users to seamlessly switch between light and dark themes, improving usability and accessibility.

Scope of Work:

Implement a theme toggle switch (Light ↔ Dark) in the application header or a prominent location.

Define and apply dark mode color palette while preserving brand identity.

Ensure color contrast meets accessibility standards in both modes.

Persist user preference using localStorage or a similar method so the selected mode remains after page reload.

Update all components and elements to adapt to both themes without layout or styling issues.

Kindly assign me this issue.