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.

frontend/src/shared/api/types.ts

@@ -89,6 +89,15 @@ export type ClientAppDto = {
 /** GET /api/apps — сгруппировано по ОС на бэкенде; отсутствующая ОС значит "нет приложений". */
 export type AppsByOs = Partial<Record<OsPlatform, ClientAppDto[]>>
 
+/** Один DTO на пользовательскую ленту и админку — у новости нет полей, скрытых от юзера. */
+export type NewsPostDto = {
+  id: string
+  title: string
+  body: string
+  createdAt: string
+  updatedAt: string | null
+}
+
 export type LinkTokenResponse = {
   deepLink: string | null
   expiresAt: string