feat: add new dashboard components and enhance UI

- Introduced new CSS variables for light theme in `globals.css` to improve visual consistency.
- Replaced `Card` component with `StatCard`, `ProgressBar`, and `MetricCard` in `DashboardStats`, `ProductivityAnalytics`, and `RecentTasks` for better modularity and reusability.
- Updated `QuickActions` to use `ActionCard` for a more cohesive design.
- Enhanced `Badge` and `Button` components with new variants for improved styling options.
- Added new UI showcase section in `UIShowcaseClient` to demonstrate the new dashboard components.

src/components/ui/index.ts

@@ -5,6 +5,13 @@ export { Alert, AlertTitle, AlertDescription } from './Alert';
 export { Input } from './Input';
 export { StyledCard } from './StyledCard';
 
+// Composants Dashboard
+export { StatCard } from './StatCard';
+export { ProgressBar } from './ProgressBar';
+export { ActionCard } from './ActionCard';
+export { TaskCard } from './TaskCard';
+export { MetricCard } from './MetricCard';
+
 // Composants existants
 export { Card, CardHeader, CardTitle, CardContent, CardFooter } from './Card';
 export { Header } from './Header';