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/Admin/Pricing/GetPricingSettingsQuery.cs

@@ -1,3 +1,4 @@
+using PnvPanel.Application.Common.Interfaces;
 using PnvPanel.Application.Common.Messaging;
 using PnvPanel.Application.Common.Models;