feat(#135): mode édition dossier + ajout co-parent (squash develop).

Wizard edit famille/AM, POST co-parent, PATCH enfants avec photo.

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

backend/src/routes/parents/dto/staff-add-co-parent-response.dto.ts

@@ -0,0 +1,23 @@
+import { ApiProperty } from '@nestjs/swagger';
+import { StatutUtilisateurType } from 'src/entities/users.entity';
+
+/** Réponse 201 POST /parents/:id/co-parent (#135). */
+export class StaffAddCoParentResponseDto {
+  @ApiProperty()
+  message: string;
+
+  @ApiProperty({ example: '2026-000043' })
+  numero_dossier: string;
+
+  @ApiProperty({ format: 'uuid', description: 'UUID du parent pivot' })
+  parent_user_id: string;
+
+  @ApiProperty({ format: 'uuid', description: 'UUID du co-parent créé' })
+  co_parent_user_id: string;
+
+  @ApiProperty({
+    enum: StatutUtilisateurType,
+    example: StatutUtilisateurType.ACTIF,
+  })
+  statut: StatutUtilisateurType;
+}