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/src/PnvPanel.Infrastructure/Persistence/AppDbContext.cs

@@ -10,6 +10,7 @@ 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;
@@ -65,6 +66,8 @@ public class AppDbContext(DbContextOptions<AppDbContext> options)
 
     public DbSet<PaymentRequest> PaymentRequests => Set<PaymentRequest>();
 
+    public DbSet<Plan> Plans => Set<Plan>();
+
     protected override void OnModelCreating(ModelBuilder modelBuilder)
     {
         base.OnModelCreating(modelBuilder);