refactor index.ts naming to auth-controller.ts for better readability

Author: sembcorpp

backend/user/src/controllers/auth/index.ts renamed to backend/user/src/controllers/auth/auth-controller.ts

@@ -1,8 +1,8 @@
 import express from 'express';
 
-import { login, logout } from '@/controllers/auth';
+import { login, logout } from '@/controllers/auth/auth-controller';
 import { limiter } from '@/lib/ratelimit';
-import { register } from '@/controllers/auth';
+import { register } from '@/controllers/auth/auth-controller';
 
 const router = express.Router();