refactor: unify date handling with utility functions

- Replaced direct date manipulations with utility functions like `getToday`, `parseDate`, and `createDateFromParts` across various components and services for consistency.
- Updated date initialization in `JiraAnalyticsService`, `BackupService`, and `DailyClient` to improve clarity and maintainability.
- Enhanced date parsing in forms and API routes to ensure proper handling of date strings.

src/components/settings/BackupSettingsPageClient.tsx

@@ -194,7 +194,7 @@ export default function BackupSettingsPageClient({ initialData }: BackupSettings
 
   const formatDate = (date: string | Date): string => {
     // Format cohérent serveur/client pour éviter les erreurs d'hydratation
-    const d = typeof date === 'string' ? new Date(date) : date;
+    const d = typeof date === 'string' ? parseDate(date) : date;
     return formatDateForDisplay(d, 'DISPLAY_MEDIUM');
   };