feat(#159): suppressions métier dossiers/parents/enfants/AM/staff.

SuppressionService + DELETE /dossiers/:numero, cascades DELETE /users et
DELETE /enfants?deleteDossier, flag sans_enfant, specs front #160.

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

backend/src/routes/dossiers/dossiers.service.spec.ts

@@ -4,6 +4,7 @@ import { DossiersService } from './dossiers.service';
 import { Parents } from 'src/entities/parents.entity';
 import { AssistanteMaternelle } from 'src/entities/assistantes_maternelles.entity';
 import { ParentsService } from '../parents/parents.service';
+import { SuppressionService } from '../suppressions/suppression.service';
 import { StatutUtilisateurType } from 'src/entities/users.entity';
 
 describe('DossiersService.listDossiers', () => {
@@ -32,6 +33,9 @@ describe('DossiersService.listDossiers', () => {
   const parentsService = {
     getDossierFamilleByNumero: jest.fn(),
   };
+  const suppressionService = {
+    countEnfantsForNumero: jest.fn().mockResolvedValue(1),
+  };
 
   beforeEach(async () => {
     const module: TestingModule = await Test.createTestingModule({
@@ -40,6 +44,7 @@ describe('DossiersService.listDossiers', () => {
         { provide: getRepositoryToken(Parents), useValue: parentsRepo },
         { provide: getRepositoryToken(AssistanteMaternelle), useValue: amRepo },
         { provide: ParentsService, useValue: parentsService },
+        { provide: SuppressionService, useValue: suppressionService },
       ],
     }).compile();
 
@@ -47,6 +52,7 @@ describe('DossiersService.listDossiers', () => {
     jest.clearAllMocks();
     parentsRepo.createQueryBuilder.mockReturnValue(parentsQb);
     amRepo.createQueryBuilder.mockReturnValue(amQb);
+    suppressionService.countEnfantsForNumero.mockResolvedValue(1);
   });
 
   it('aggregates famille (pivot+co-parent) and AM, sorts a_valider first', async () => {