feat(#135): POST /parents/:id/co-parent — ajout co-parent foyer.

API staff pour foyer mono-parent : compte actif, liens + enfants,
mail création MDP. Mini-specs front/back dans docs/tmp.

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

backend/src/routes/parents/parents.controller.spec.ts

@@ -11,6 +11,7 @@ describe('ParentsController', () => {
   let controller: ParentsController;
   const authServiceMock = {
     createParentDossierStaff: jest.fn(),
+    addCoParentStaff: jest.fn(),
   };
   const parentsServiceMock = {};
   const userServiceMock = {};
@@ -77,4 +78,27 @@ describe('ParentsController', () => {
     expect(res.enfant_ids).toEqual(['e1']);
     expect(res.statut).toBe(StatutUtilisateurType.ACTIF);
   });
+
+  it('addCoParent delegates to authService.addCoParentStaff', async () => {
+    authServiceMock.addCoParentStaff.mockResolvedValue({
+      message: 'ok',
+      numero_dossier: '2026-000043',
+      parent_user_id: 'p1',
+      co_parent_user_id: 'p2',
+      statut: StatutUtilisateurType.ACTIF,
+    });
+
+    const body = {
+      email: 'coparent@test.fr',
+      prenom: 'Thomas',
+      nom: 'MARTIN',
+      telephone: '0678456789',
+      meme_adresse: true,
+    };
+
+    const res = await controller.addCoParent('p1', body as any);
+    expect(authServiceMock.addCoParentStaff).toHaveBeenCalledWith('p1', body);
+    expect(res.co_parent_user_id).toBe('p2');
+    expect(res.statut).toBe(StatutUtilisateurType.ACTIF);
+  });
 });