Refactor pricing endpoints and enhance support for pricing retrieval

- Added a new endpoint `/api/support/pricing` to allow users to retrieve pricing information, making it accessible for role request dialogs.
- Introduced the `GetSupportPricing` method to handle pricing queries, ensuring that pricing data is available to non-admin users.
- Updated frontend components to integrate the new pricing retrieval functionality, displaying estimated costs based on user-selected configurations.
- Removed the `PricingSettingsDto` as it is no longer needed, streamlining the pricing data structure.
- Enhanced API documentation to reflect the new endpoint and its usage in the support context.

backend/src/PnvPanel.Application/Support/GetSupportPricing/GetSupportPricingQuery.cs

@@ -0,0 +1,9 @@
+using PnvPanel.Application.Common.Interfaces;
+using PnvPanel.Application.Common.Messaging;
+using PnvPanel.Application.Common.Models;
+
+namespace PnvPanel.Application.Support.GetSupportPricing;
+
+/// <summary>Справочная цена конфига для заявки на роль (не редактирование, только чтение) — в отличие
+/// от GetPricingSettingsQuery (Admin/Pricing), доступна любому активированному пользователю.</summary>
+public sealed record GetSupportPricingQuery : IQuery<Result<PricingSettingsDto>>, IRequiresActivation;

backend/src/PnvPanel.Application/Support/GetSupportPricing/GetSupportPricingQueryHandler.cs

@@ -0,0 +1,27 @@
+using Microsoft.EntityFrameworkCore;
+using PnvPanel.Application.Common.Interfaces;
+using PnvPanel.Application.Common.Messaging;
+using PnvPanel.Application.Common.Models;
+
+namespace PnvPanel.Application.Support.GetSupportPricing;
+
+public sealed class GetSupportPricingQueryHandler(IAppDbContext dbContext)
+    : IQueryHandler<GetSupportPricingQuery, Result<PricingSettingsDto>>
+{
+    public async Task<Result<PricingSettingsDto>> Handle(
+        GetSupportPricingQuery query,
+        CancellationToken cancellationToken
+    )
+    {
+        var settings = await dbContext
+            .PricingSettings.AsNoTracking()
+            .FirstOrDefaultAsync(cancellationToken);
+
+        // Ещё не сидировано/не сохранено ни разу — цена не задана, а не ошибка.
+        return Result.Success(
+            settings is null
+                ? new PricingSettingsDto(null, null, null)
+                : PricingSettingsDto.FromDomain(settings)
+        );
+    }
+}