Implement billing functionality and enhance role management

- Introduced billing capabilities, allowing users to request payments for subscription periods (3/6/12 months) with admin approval via Telegram.
- Updated role management to include a `BillingEnabled` property, preventing billing for admin roles.
- Enhanced the `CreateRoleCommand` and `UpdateRoleCommand` to accept billing parameters, ensuring proper handling during role creation and updates.
- Added new endpoints for billing management and integrated billing checks into VPN config creation to enforce payment requirements.
- Updated related services, models, and tests to support the new billing features, ensuring comprehensive coverage and functionality.
- Enhanced documentation to reflect the new billing processes and role management changes.

backend/tests/PnvPanel.Application.Tests/Auth/GetCurrentUserQueryHandlerTests.cs

@@ -55,7 +55,10 @@ public class GetCurrentUserQueryHandlerTests
             false,
             3,
             RoleQuota.Unlimited,
-            "sub-token"
+            "sub-token",
+            false,
+            null,
+            false
         );
         _identityService.GetProfileAsync(userId, Arg.Any<CancellationToken>()).Returns(profile);
         _identityService