feat: complete Phase 3 of service refactoring

- Marked tasks in `TODO.md` as completed for moving backup-related files to the `data-management` directory and correcting imports across the codebase.
- Updated imports in `backup-manager.ts`, API routes, and various components to reflect the new structure.
- Removed obsolete `backup.ts` and `backup-scheduler.ts` files to streamline the codebase.
- Added new tasks in `TODO.md` for future cleaning and organization of service imports.

src/services/core/system-info.ts

@@ -125,7 +125,7 @@ export class SystemInfoService {
   private static async getBackupCount(): Promise<number> {
     try {
       // Import dynamique pour éviter les dépendances circulaires
-      const { backupService } = await import('../backup');
+      const { backupService } = await import('../data-management/backup');
       const backups = await backupService.listBackups();
       return backups.length;
     } catch (error) {

src/services/data-management/backup.ts

@@ -1,8 +1,8 @@
 import { promises as fs } from 'fs';
 import path from 'path';
-import { prisma } from './core/database';
-import { userPreferencesService } from './core/user-preferences';
-import { BackupUtils } from '../lib/backup-utils';
+import { prisma } from '../core/database';
+import { userPreferencesService } from '../core/user-preferences';
+import { BackupUtils } from '../../lib/backup-utils';
 import { getToday } from '@/lib/date-utils';
 
 export interface BackupConfig {