[FEATURE] Add built-in user roles.

### Describe the feature

Add basic built-in users, such as administrators, read-only users, and regular users.

### Motivation

In order to meet the customer's needs

### Describe the solution

| name | privilege |
| :---- | :---- |
| admin | ALL |
| regular | CreateCatalog |
| readonly | `UseCatalog，UseSchema，SelectTable`，`ConsumeTopic`，`ReadFileset`，`ReadModel` |

### Additional context

_No response_

The issue names no files, tests, or entry points. Start by locating the project's authorization and privilege definitions, then determine how built-in users are represented and assigned permissions. Done should include admin, regular, and readonly roles with the listed privilege mappings, plus coverage for their behavior.

Written by the indexing model from the issue text.