fix(upload): markAllAsTouched au submit pour afficher les erreurs de validation

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Co-Authored-By: Claude <noreply@anthropic.com>
Co-Authored-By: Happy <yesreply@happy.engineering>

front-public/src/app/pages/upload/upload.component.ts

@@ -726,6 +726,7 @@ export class UploadComponent implements OnInit {
 
   onSubmit() {
     const files = this.selectedFiles();
+    this.metaForm.markAllAsTouched();
     if (files.length === 0 || this.metaForm.invalid) return;
 
     this.uploading.set(true);