Enhance user plan management and update related endpoints

- Added new configuration options for user plans in `.env.example`, including `Plans__MaxCustomConfigCount` and `Plans__MinCustomConfigCount`.
- Introduced `MapPlanEndpoints` in `Program.cs` to handle plan-related API routes.
- Implemented `SetUserPlan` endpoint in `RoleEndpoints` to allow admins to assign plans to users.
- Removed deprecated role request approval endpoints from `AdminSupportEndpoints`.
- Updated `ITelegramNotifier` and related classes to reflect changes in role request handling and payment notifications.
- Refactored role management commands to remove `MaxConfigs` and focus on `MaxIpLimit` and billing settings.
- Enhanced billing request handling to accommodate plan changes instead of role changes.
- Updated various interfaces and command handlers to support new plan management features.

backend/tests/PnvPanel.Application.Tests/Configs/Rotate/RotateVpnConfigCommandHandlerTests.cs

@@ -16,6 +16,7 @@ using PnvPanel.Domain.Inbounds;
 using PnvPanel.Domain.Instructions;
 using PnvPanel.Domain.News;
 using PnvPanel.Domain.Nodes;
+using PnvPanel.Domain.Plans;
 using PnvPanel.Domain.Pricing;
 using PnvPanel.Domain.Support;
 using PnvPanel.Domain.Telegram;
@@ -48,6 +49,7 @@ public sealed class ThrowingSaveDbContext(AppDbContext inner) : IAppDbContext
     public DbSet<PricingDiscountTier> PricingDiscountTiers => inner.PricingDiscountTiers;
     public DbSet<BillingSettings> BillingSettings => inner.BillingSettings;
     public DbSet<PaymentRequest> PaymentRequests => inner.PaymentRequests;
+    public DbSet<Plan> Plans => inner.Plans;
     public DatabaseFacade Database => inner.Database;
 
     public Task<int> SaveChangesAsync(CancellationToken cancellationToken) =>
@@ -68,6 +70,7 @@ public class RotateVpnConfigCommandHandlerTests
             true,
             false,
             3,
+            null,
             RoleQuota.Unlimited,
             "sub-token",
             false,