`username` can be repeat when using `user.create` controller
### Node Version

20.11.1

### NPM/Yarn/PNPM Version

10.2.4

### Strapi Version

5.9.0

### Operating System

Windows 11

### Database

MySQL

### Javascript or Typescript

Typescript

### Reproduction URL

_No response_

### Bug Description

When using controller api to create a user `/api/users`, the controller does not test username unique, you can create multiple users with a same username.

When using the admin dashboard to create  a user, you will get an error message  'username exist' if the username is not unique.

### Steps to Reproduce

Here is the translated content from English to English (as the original text is already in English):

1. **content-type.ts** not force the column unique (default config)
   ```ts
   {
     // ...
     "attributes": {
       "username": {
          // ...
         "unique": true,
          // ...
         "column": {
           "unique": false
         }
       },
       // ...
     }
   }
   ```

2. **curl**
   ```bash
   curl -X POST 'http://localhost:5000/api/users' 
   -H 'Content-Type: application/json' 
   -d '{
       "username": "11111",
       "email": "111@qqq.com",
       "password": "11111111",
       "role": {
           "connect": [
               {
                   "id": 1
               }
           ]
       }
   }'
   ```

3. Repeat step 1 with a different email.

4. Received response 201 success.

### Expected Behavior

response 400 forbidden error with message 'Username  exist'

### Logs

```shell

```

### Code Snippets

_No response_

### Media

![Image](https://github.com/user-attachments/assets/94275709-d03f-4c81-beb2-8835d759213a)

### Additional information

_No response_

### Confirmation Checklist

- [x] I have checked the existing [issues](https://github.com/strapi/strapi/issues) for duplicates.
- [x] I agree to follow this project's [Code of Conduct](https://github.com/strapi/strapi/blob/develop/CODE_OF_CONDUCT.md).