Add news feature with CRUD operations and real-time notifications

- Implemented news management functionality, allowing admins to create, read, update, and delete news posts.
- Introduced a new SignalR event for broadcasting news updates to all connected clients.
- Updated API documentation to include new endpoints for news management.
- Enhanced frontend with a dedicated news page and admin interface for managing news posts.
- Added necessary localization for news-related terms in both Russian and English.

backend/src/PnvPanel.Api/Program.cs

@@ -151,9 +151,11 @@ app.MapInboundEndpoints();
 app.MapConfigEndpoints();
 app.MapSubscriptionEndpoints();
 app.MapAppEndpoints();
+app.MapNewsEndpoints();
 app.MapAdminUserEndpoints();
 app.MapAdminStatsEndpoints();
 app.MapAdminAppEndpoints();
+app.MapAdminNewsEndpoints();
 app.MapTelegramEndpoints();
 
 app.MapHub<PanelHub>("/hubs/panel");