feat: add data export functionality to settings page and update admin reports table

- Introduced "Export Data" card in settings for exporting user data as a JSON file.
- Added `exportData` method to `UserService` for handling data export requests.
- Updated admin reports table with a new "Cible" column to display target information.

frontend/src/app/(dashboard)/admin/reports/page.tsx

@@ -104,6 +104,7 @@ export default function AdminReportsPage() {
 						<TableHeader>
 							<TableRow>
 								<TableHead>Signalé par</TableHead>
+								<TableHead>Cible</TableHead>
 								<TableHead>Raison</TableHead>
 								<TableHead>Description</TableHead>
 								<TableHead>Statut</TableHead>
@@ -114,13 +115,13 @@ export default function AdminReportsPage() {
 						<TableBody>
 							{loading ? (
 								<TableRow>
-									<TableCell colSpan={5} className="text-center py-8">
+									<TableCell colSpan={7} className="text-center py-8">
 										Chargement...
 									</TableCell>
 								</TableRow>
 							) : reports.length === 0 ? (
 								<TableRow>
-									<TableCell colSpan={5} className="text-center py-8">
+									<TableCell colSpan={7} className="text-center py-8">
 										Aucun signalement trouvé.
 									</TableCell>
 								</TableRow>