Fix dark mode functionality, accessibility support, and merge conflicts

[SRSoham]

Summary

This PR rebuilds the dark mode implementation cleanly on top of the latest main branch and resolves previous merge conflict issues.

Changes Made

• Restored functional dark mode toggle
• Added theme persistence using localStorage
• Added accessibility improvements:
  • aria-label
  • aria-pressed
• Added reduced motion support
• Fixed merge conflict corruption in script.js
• Cleaned duplicate CSS blocks and conflicting styles
• Improved dark mode styling for:
  • forms
  • cards
  • buttons
  • inputs
  • skill chips
  • sections/navbar/footer

Testing

Tested locally and verified:

• dark mode toggles correctly
• theme persists after refresh
• no layout breaking
• responsive layout works correctly
• form submission works properly
• no console errors

Previous PR Reference

This PR supersedes the earlier conflicted PR:
#350

The previous branch encountered repeated merge conflicts after overlapping updates landed in the same sections. This branch rebuilds the implementation cleanly on top of the latest main branch.

[vercel]

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[komalharshita]

Looks good to merge!