Build Core Dashboard + GitHub Integration

## 📄 Description

Now that the project structure is ready, this issue covers the **basic foundation of the Developer Dashboard**, including layout, navigation, and initial GitHub data display using OAuth.

This should set the stage for other widgets to be added later.

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## ✅ Tasks

- [ ] Create a basic **dashboard layout** using `components/Layout.tsx`
- Sidebar (if needed)
- Header bar with user info
- Main content area
- [ ] Display GitHub profile data:
- Name, avatar, username
- Public repo count
- Followers & following
- [ ] Show recent GitHub repositories
- Name, description, stars, link
- [ ] Use **GitHub GraphQL API** via personal access token (or via Clerk JWT if scoped)
- [ ] Handle loading and error states
- [ ] Ensure layout is **responsive** (mobile + desktop)

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## 🧠 References

- [GitHub GraphQL API Docs](https://docs.github.com/en/graphql)
- [Clerk GitHub Auth Guide](https://clerk.com/docs/authentication/social-providers/github)
- [Next.js Layout Docs](https://nextjs.org/docs/pages/building-your-application/routing/pages-and-layouts)

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## 💡 Notes

- This is a **foundational feature** — keep the code modular and clean
- More GitHub stats (e.g., contribution graph, PRs) will come in future issues
- For now, just fetch and display user profile + repos

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📌 **Comment below if you'd like to work on this. Tag your PR with `Closes #` when ready.**

Start with components/Layout.tsx and the linked Next.js layout, GitHub GraphQL API, and Clerk GitHub authentication documentation. Done means the responsive dashboard shows the authenticated user's profile, repository list, loading and error states, with the requested GitHub data and navigation foundation working on mobile and desktop.

Written by the indexing model from the issue text.