Add theme toggle

[puneetnith28]

Summary

Adds a light/dark theme toggle to the extension popup.
The toggle allows users to switch themes at runtime and persists the selected preference across sessions using chrome.storage.sync and localStorage.

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What Changed

Feature: ThemeToggle component

• Added ThemeToggle.tsx component.
• Allows users to switch between light and dark themes.
• Applies the selected theme immediately at runtime.

Persistence

• Stores theme preference in:
  • chrome.storage.sync (for extension sync across browsers/devices)
  • localStorage (as a fallback)
• Automatically loads the saved theme on popup open.

Theming

• Uses CSS variables for theme colors.
• Ensures consistent color updates across the popup.

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Screenshots-------------------------------->>>>>>>>>>>>>>>>

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Closes:---->> #28

[puneetnith28]

Hello @akash-kumar-dev
Please review this PR and let me know if any changes are required !!
Thanks !!