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/analytics.ts

@@ -1,5 +1,6 @@
 import { Task, TaskStatus, TaskPriority, TaskSource } from '@/lib/types';
 import { prisma } from './database';
+import { getToday, parseDate, subtractDays, addDays } from '@/lib/date-utils';
 
 export interface ProductivityMetrics {
   completionTrend: Array<{
@@ -42,8 +43,8 @@ export class AnalyticsService {
    */
   static async getProductivityMetrics(timeRange?: TimeRange): Promise<ProductivityMetrics> {
     try {
-      const now = new Date();
-      const defaultStart = new Date(now.getTime() - 30 * 24 * 60 * 60 * 1000); // 30 jours
+      const now = getToday();
+      const defaultStart = subtractDays(now, 30); // 30 jours
       
       const start = timeRange?.start || defaultStart;
       const end = timeRange?.end || now;
@@ -99,7 +100,7 @@ export class AnalyticsService {
     const trend: Array<{ date: string; completed: number; created: number; total: number }> = [];
     
     // Générer les dates pour la période
-    const currentDate = new Date(start);
+    const currentDate = new Date(start.getTime());
     while (currentDate <= end) {
       const dateStr = currentDate.toISOString().split('T')[0];
       
@@ -116,7 +117,7 @@ export class AnalyticsService {
       
       // Total cumulé jusqu'à ce jour
       const totalUntilThisDay = tasks.filter(task => 
-        new Date(task.createdAt) <= currentDate
+        task.createdAt <= currentDate
       ).length;
 
       trend.push({
@@ -156,7 +157,7 @@ export class AnalyticsService {
     
     // Convertir en format pour le graphique
     weekGroups.forEach((count, weekKey) => {
-      const weekDate = new Date(weekKey);
+      const weekDate = parseDate(weekKey);
       weeklyData.push({
         week: `Sem. ${this.getWeekNumber(weekDate)}`,
         completed: count,
@@ -209,10 +210,10 @@ export class AnalyticsService {
    * Calcule les statistiques hebdomadaires
    */
   private static calculateWeeklyStats(tasks: Task[]) {
-    const now = new Date();
+    const now = getToday();
     const thisWeekStart = this.getWeekStart(now);
-    const lastWeekStart = new Date(thisWeekStart.getTime() - 7 * 24 * 60 * 60 * 1000);
-    const lastWeekEnd = new Date(thisWeekStart.getTime() - 1);
+    const lastWeekStart = subtractDays(thisWeekStart, 7);
+    const lastWeekEnd = subtractDays(thisWeekStart, 1);
     
     const thisWeekCompleted = tasks.filter(task => 
       task.completedAt && 
@@ -243,7 +244,7 @@ export class AnalyticsService {
    * Obtient le début de la semaine pour une date
    */
   private static getWeekStart(date: Date): Date {
-    const d = new Date(date);
+    const d = new Date(date.getTime());
     const day = d.getDay();
     const diff = d.getDate() - day + (day === 0 ? -6 : 1); // Lundi = début de semaine
     return new Date(d.setDate(diff));