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/Endpoints/AdminNewsEndpoints.cs

@@ -0,0 +1,52 @@
+using PnvPanel.Api.Common;
+using PnvPanel.Application.Admin.News;
+using PnvPanel.Application.Common.Messaging;
+using PnvPanel.Application.Common.Models;
+using PnvPanel.Application.News;
+using PnvPanel.Infrastructure.Identity;
+
+namespace PnvPanel.Api.Endpoints;
+
+public static class AdminNewsEndpoints
+{
+    public static IEndpointRouteBuilder MapAdminNewsEndpoints(this IEndpointRouteBuilder app)
+    {
+        var admin = app.MapGroup("/api/admin/news")
+            .WithTags("Admin.News")
+            .RequireAuthorization(policy => policy.RequireRole(RoleNames.Admin));
+
+        admin.MapGet("", ListAdminNews).Produces<PagedList<NewsPostDto>>();
+        admin.MapPost("", CreatePost).Produces<NewsPostDto>();
+        admin.MapPut("/{id:guid}", UpdatePost).Produces<NewsPostDto>();
+        admin.MapDelete("/{id:guid}", DeletePost).Produces(StatusCodes.Status204NoContent);
+
+        return app;
+    }
+
+    private static async Task<IResult> ListAdminNews(int page, int pageSize, ISender sender, CancellationToken cancellationToken)
+    {
+        var result = await sender.Send(new ListAdminNewsQuery(page, pageSize), cancellationToken);
+        return result.ToHttpResult();
+    }
+
+    private static async Task<IResult> CreatePost(CreatePostCommand command, ISender sender, CancellationToken cancellationToken)
+    {
+        var result = await sender.Send(command, cancellationToken);
+        return result.ToHttpResult();
+    }
+
+    private static async Task<IResult> UpdatePost(Guid id, UpdatePostBody body, ISender sender, CancellationToken cancellationToken)
+    {
+        var command = new UpdatePostCommand(id, body.Title, body.Body);
+        var result = await sender.Send(command, cancellationToken);
+        return result.ToHttpResult();
+    }
+
+    private static async Task<IResult> DeletePost(Guid id, ISender sender, CancellationToken cancellationToken)
+    {
+        var result = await sender.Send(new DeletePostCommand(id), cancellationToken);
+        return result.ToHttpResult();
+    }
+}
+
+public sealed record UpdatePostBody(string Title, string Body);