User Module | Register Feature

### DAO:

- [x] createUser()

### Service:

- [x] registerUser()

### ServiceTest:
TestRegisterFeature:

- [x] testRegistrationSuccess
- [x] testRegistrationfail

### Estimation:
- 5 hrs

```mermaid
flowchart TD
A[Start]
B[User inputs name,mobileNo,email,password]
C[Validate Information]
D[Create User Account]
F[Finish]

A --> B
B --> C
C -->|Valid| D
C -->|Invalid| B
D --> F

```

Locate the User DAO's createUser() and the Service's registerUser() entry points, then read TestRegisterFeature with testRegistrationSuccess and testRegistrationfail. Confirm that registration validates name, mobile number, email, and password, creates an account for valid input, rejects invalid input, and that both tests pass.

Written by the indexing model from the issue text.