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.Application/Configs/Create/CreateVpnConfigCommandHandler.cs

@@ -44,7 +44,7 @@ public sealed class CreateVpnConfigCommandHandler(
 
         var addResult = await gateway.AddClientAsync(
             node, inbound.RemoteInboundId, inbound.Protocol, config.ClientEmail,
-            config.Label ?? config.ClientEmail, cancellationToken);
+            config.Label ?? config.ClientEmail, profile.MaxIpLimit, cancellationToken);
 
         if (!addResult.IsSuccess)
         {