Refactor authentication and theme context usage

- Moved authentication hooks and context to a dedicated hooks directory.
- Updated imports in various components and pages to use the new hooks.
- Created AuthContext and ThemeContext for better state management.
- Refactored ThemeProvider to utilize the new ThemeContext.
- Cleaned up sidebar and button components for consistency and readability.
- Ensured all components are using the latest context and hooks for authentication and theme management.

src/pages/RegisterPage.tsx

@@ -4,7 +4,7 @@ import { Button } from '@/components/ui/button'
 import { Input } from '@/components/ui/input'
 import { Label } from '@/components/ui/label'
 import { Card, CardContent, CardDescription, CardHeader, CardTitle } from '@/components/ui/card'
-import { useAuth } from '@/contexts/AuthContext'
+import { useAuth } from '@/hooks/use-auth'
 import { authService } from '@/services/auth'
 
 export function RegisterPage() {