feat: add user operations to backend

backend/src/user/user.module.ts

@@ -1,7 +1,9 @@
 import { Module } from "@nestjs/common";
 import { UserController } from "./user.controller";
+import { UserSevice } from "./user.service";
 
 @Module({
+  providers: [UserSevice],
   controllers: [UserController],
 })
 export class UserModule {}