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/Support/CreateRoleRequestTicketCommandHandlerTests.cs

@@ -23,7 +23,7 @@ public class CreateRoleRequestTicketCommandHandlerTests
         var currentUser = FakeCurrentUser.Authenticated(userId, "alice");
         _roleService
             .ListRolesAsync(Arg.Any<CancellationToken>())
-            .Returns(new List<RoleDto> { new(roleId, "premium", 5, 2, false) });
+            .Returns(new List<RoleDto> { new(roleId, "premium", 5, 2, false, false) });
 
         var handler = new CreateRoleRequestTicketCommandHandler(
             dbContext,
@@ -61,7 +61,7 @@ public class CreateRoleRequestTicketCommandHandlerTests
         var currentUser = FakeCurrentUser.Authenticated(Guid.NewGuid());
         _roleService
             .ListRolesAsync(Arg.Any<CancellationToken>())
-            .Returns(new List<RoleDto> { new(roleId, "admin", -1, -1, true) });
+            .Returns(new List<RoleDto> { new(roleId, "admin", -1, -1, true, false) });
 
         var handler = new CreateRoleRequestTicketCommandHandler(
             dbContext,