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/services/jira-anomaly-detection.ts

@@ -4,6 +4,7 @@
  */
 
 import { JiraAnalytics, SprintVelocity, CycleTimeByType, AssigneeWorkload } from '@/lib/types';
+import { getToday } from '@/lib/date-utils';
 
 export interface JiraAnomaly {
   id: string;
@@ -44,7 +45,7 @@ export class JiraAnomalyDetectionService {
    */
   async detectAnomalies(analytics: JiraAnalytics): Promise<JiraAnomaly[]> {
     const anomalies: JiraAnomaly[] = [];
-    const timestamp = new Date().toISOString();
+    const timestamp = getToday().toISOString();
 
     // 1. Détection d'anomalies de vélocité
     const velocityAnomalies = this.detectVelocityAnomalies(analytics.velocityMetrics, timestamp);