Fix the build error and implement dark theme into the landing page

[CodeMaverick-143]

Fixes Issue #675

This PR adds a complete dark theme implementation to the Landing Page while preserving the original design and functionality.

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Changes Made

• Added darkMode: 'class' to tailwind.config.js
• Created ThemeContext.jsx to manage theme state with React Context API
• Implemented ThemeToggle component with sun/moon icons
• Added dark mode variants to LandingPage.jsx using Tailwind dark: classes
• Updated Navbar.jsx with dark mode styling and theme toggle buttons
• Added localStorage persistence for user theme preference
• Implemented system color scheme detection using prefers-color-scheme

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Features

• Toggle between light and dark themes using a dedicated button
• Theme preference is saved in localStorage
• Detects system preference on initial load
• Consistent color scheme across all UI elements
• Maintains all animations, transitions, and original layout

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Screenshots

Light Mode: Original design preserved
Dark Mode: Dark background with adjusted text colors for readability

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Technical Notes

• No changes were made to the existing component structure or file hierarchy
• All GSAP and Framer Motion animations remain untouched
• Only color schemes were modified — no changes to layout or spacing
• Used Tailwind CSS dark mode variants for all styling changes

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Verification Checklist

• Dark/Light theme toggle works correctly
• User preference persists after page reload
• System theme detection functions properly
• No design regressions in layout or animations

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[CodeMaverick-143]

@1ilit Can you please review it.