Issue Title: Add Dark Mode Feature for Enhanced User Experience

[diya-kishore]

Description:
To improve user comfort and modernize our interview prep app, we propose adding a dark mode feature. This option will:

Reduce Eye Strain: Ideal for long study sessions.
Conserve Battery Life: Especially beneficial for OLED screen users.
Align with User Preferences: A popular feature in many applications today.

Proposed Implementation:
Create a toggle switch for easy mode switching.
Ensure all UI elements are readable in both light and dark modes.
Store user preference in local storage for a seamless experience.
By implementing dark mode, we can significantly enhance user satisfaction and keep pace with current design trends.

[Xeven777]

Assigned ✅ go ahead ☺️