Fix: Prevent theme flicker on initial render

[pandaabinash99]

Summary:

This update ensures the correct theme (light/dark) is applied before the first paint, preventing the flicker that occurred during initial page load.

• Added a small inline script in layout.js to set the theme class on the element before React hydration.
• Simplified ThemeProvider logic to avoid redundant theme initialization in useEffect.
• Improved overall user experience and visual consistency on page load.

Issue Link:

Fixes #32

PR Checks:

• Code is properly formatted (executed make pre-push command).
• No ESLint warnings (verified with make pre-push command).
• UI Changes are responsive (checked in the responsive view).
• Performance is maintained (Lighthouse report reviewed).
• User experience (UX) considerations are met.
• Accessibility is supported (validated with accessibility tools).