Add a dark-mode toggle control to TopHeader.tsx (styling only)

[Akatenvictor]

Context

Tailwind CSS 4 is configured but the app has no dark mode despite the dependency being available. As a first step, add a toggle UI control in TopHeader.tsx that switches a dark class on the html/body element and persists the choice to localStorage.

Acceptance Criteria

• Toggle button in TopHeader.tsx switches dark class on the root html element
• Preference persists across reloads via localStorage
• Toggle has accessible label and visible focus state

[blockchainrafik]

@blockchainrafik has applied to work on this issue as part of the Stellar Wave Program's 6th wave.

Good day maintainer,
I will like to work on this issue,
With years of experience in software engineering, Getting this issue fixed without regression is assured.
ETA: 2hrs

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[Samuel-21-eng]

@Samuel-21-eng has applied to work on this issue as part of the Stellar Wave Program's 6th wave.

Hi maintainer, I would love to work on this issue

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[emickwrld]

@emickwrld has applied to work on this issue as part of the Stellar Wave Program's 6th wave.

Hi, I’m a smart contract and a full-stack web developer, I have read through the issue and it’s something I’m capable of doing. Please assign me this work.

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[VictorEzenma]

@VictorEzenma has applied to work on this issue as part of the Stellar Wave Program's 6th wave.

Hi maintainer, I would love to contribute to this by applying the necessary fixes and improvements to get it done

ℹ️ Repo Maintainers: To accept this application, review their application or assign @VictorEzenma to this issue.

[nonggde]

Submitted PR: #77

[drips-wave]

Congratulations, @abayomicornelius! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on July 30, 2026.

🧑‍💻 @abayomicornelius: Please resolve the issue such that the repo's maintainers have enough time to review your contribution before the due date. You'll earn Points for completing the issue on-time, which will make you eligible for a share of the Stellar Wave Program's reward pool.

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