feat(user): implement User entity, CRUD operations, Swagger docs, and tests

[phertyameen]

Description

This PR introduces the core User module with full CRUD functionality, validation, API documentation, and unit tests.

Related Issues

Closes #365

Changes Made

• Defined User entity with id, email, passwordHash, role, and createdAt fields.

• Implemented UserService with CRUD operations and secure password hashing using bcrypt.

• Created UserController exposing the following endpoints:

  • GET /users → fetch all users
  • POST /users → create new user (password auto-hashed)
  • PATCH /users/:id → update user details (rehash password if changed)
  • DELETE /users/:id → delete user

• Added DTOs (CreateUserDto, UpdateUserDto) with validation and Swagger decorators.

• Enhanced controller with Swagger documentation decorators for clear API docs.

• Added unit tests for both service and controller using Jest.

How to Test

Screenshots (if applicable)

Checklist

• My code follows the project's coding style.
• I have tested these changes locally.
• Documentation has been updated where necessary.
• Users can be created, retrieved, updated, and deleted via API.
• Passwords are hashed before storage.
• API documentation is available via Swagger.
• Unit tests validate core functionality.

[BigBen-7]

LGTM