feat: admin creation modal and backend fixes for user updates (#96)

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

backend/src/routes/user/dto/update_gestionnaire.dto.ts

@@ -1,4 +1,10 @@
-import { PartialType } from "@nestjs/swagger";
+import { PartialType, ApiProperty } from "@nestjs/swagger";
 import { CreateUserDto } from "./create_user.dto";
+import { IsOptional, IsUUID } from "class-validator";
 
-export class UpdateGestionnaireDto extends PartialType(CreateUserDto) {}
+export class UpdateGestionnaireDto extends PartialType(CreateUserDto) {
+  @ApiProperty({ required: false, description: 'ID du relais de rattachement' })
+  @IsOptional()
+  @IsUUID()
+  relaisId?: string;
+}