Create dashboard with repository and file browsing
- Build Header component with user info and logout button
- Create RepoSelector with sorting options (updated, created, name)
- Implement FileTree with recursive folder expansion
* Shows file/folder icons
* Highlights selected file
* Supports nested directory structure
- Build main Dashboard component with:
* Three-column layout (sidebar + main content)
* Repository selection interface
* File tree navigation
* Empty states for no repo/file selected
* Loading states with skeleton animations
* Placeholder for editor (Phase 2)
- Set up React Query provider for data management
- Use client:only directive for React hydration
- Build test successful