feat: add theme support

[anchal125]

Description

Added light and dark theme support to the application. Users can switch between themes, and the UI updates accordingly.

Related Issue

Closes #2

Type of Change

• Bug fix
• New feature
• UI/UX improvement
• Documentation update
• Code improvement/refactoring

Changes Made

• Added light and dark theme support.
• Added a theme toggle for switching between light and dark modes.
• Added theme-specific CSS variables and styling.
• Ensured the UI components and footer adapt correctly to the selected theme.

Screenshots

Testing

• Tested the theme toggle locally.
• Verified that both light and dark themes are applied correctly.
• Checked the UI across different sections of the application.
• Verified that the application works without console errors.
• Tested the responsive layout after applying the theme changes.

Checklist

Before submitting this pull request:

• My changes address the linked issue.
• I tested the changes locally.
• The application works without console errors.
• Existing functionality still works.
• The design remains responsive.
• I did not include unrelated changes.