Implement role and user management enhancements

- Added MaxIpLimit to roles, allowing for the configuration of simultaneous IP limits for users.
- Updated role creation and update commands to include MaxIpLimit, ensuring proper handling in the application logic.
- Enhanced user management by introducing a DELETE endpoint for user accounts, with appropriate checks to prevent self-deletion.
- Updated documentation to reflect changes in role and user management, clarifying the new IP limit functionality and user deletion process.
- Adjusted related tests to cover new functionality and ensure robust validation of role and user management features.

backend/src/PnvPanel.Api/Endpoints/RoleEndpoints.cs

@@ -38,7 +38,7 @@ public static class RoleEndpoints
 
     private static async Task<IResult> UpdateRole(Guid id, UpdateRoleBody body, ISender sender, CancellationToken cancellationToken)
     {
-        var result = await sender.Send(new UpdateRoleCommand(id, body.MaxConfigs), cancellationToken);
+        var result = await sender.Send(new UpdateRoleCommand(id, body.MaxConfigs, body.MaxIpLimit), cancellationToken);
         return result.ToHttpResult();
     }
 
@@ -55,6 +55,6 @@ public static class RoleEndpoints
     }
 }
 
-public sealed record UpdateRoleBody(int MaxConfigs);
+public sealed record UpdateRoleBody(int MaxConfigs, int MaxIpLimit);
 
 public sealed record ChangeUserRoleBody(Guid RoleId);