feat(#140): dashboard admin ch.6 — fiche parent, enfants, affiliation

Back: PATCH /parents/:id/fiche, attach/detach enfant, GET /enfants enrichi.
Front: modale parent éditable, onglet Enfants, fiche enfant, UserService.

Couvre doc 28 §6.1–6.2 ; tickets liés #115 #116 #130 #131 #137 #138.
Hors scope: fiche AM (#131), création admin (#129).

Co-authored-by: Cursor <cursoragent@cursor.com>

backend/src/routes/enfants/enfants.service.ts

@@ -78,10 +78,10 @@ export class EnfantsService {
     return this.findOne(child.id, currentUser);
   }
 
-  // Liste des enfants
+  // Liste des enfants (admin/gestionnaire)
   async findAll(): Promise<Children[]> {
     return this.childrenRepository.find({
-      relations: ['parentLinks'],
+      relations: ['parentLinks', 'parentLinks.parent', 'parentLinks.parent.user'],
       order: { last_name: 'ASC', first_name: 'ASC' },
     });
   }