FEAT: BE - Authentication routes

[sergeKashkin]

The purpose of this task is to create authentication routes for login and sign-up.

1. Create new controller - auth.controller.ts
2. Under this controller, implement 2 routes:
3. POST auth/sign-up - body - { email: string; password: string; }
4. POST auth/login - body - { email: string; password: string; }
5. Create authentication service under auth.service.ts file.
6. Make sure this service implements 2 methods - login(email: string, password: string), signup(email: string; password: string)
7. Use the described methods under corresponding controller handlers.
8. We'll continue with the logic later.