feat: remove TaskStats from HomePageClient and Header components

- Eliminated `initialStats` prop from `HomePageClient` and `KanbanPageClient` to streamline data handling.
- Updated `Header` and `HeaderContainer` components to remove references to `stats`, enhancing clarity and reducing unnecessary complexity.
- Adjusted `useTasks` hook to make `stats` optional, ensuring compatibility with the updated components.

src/app/page.tsx

@@ -8,9 +8,8 @@ export const dynamic = 'force-dynamic';
 
 export default async function HomePage() {
   // SSR - Récupération des données côté serveur
-  const [initialTasks, initialStats, initialTags, initialPreferences] = await Promise.all([
+  const [initialTasks, initialTags, initialPreferences] = await Promise.all([
     tasksService.getTasks(),
-    tasksService.getTaskStats(),
     tagsService.getTags(),
     userPreferencesService.getAllPreferences()
   ]);
@@ -18,7 +17,6 @@ export default async function HomePage() {
   return (
     <HomePageClient 
       initialTasks={initialTasks}
-      initialStats={initialStats}
       initialTags={initialTags}
       initialPreferences={initialPreferences}
     />