Add metadata management for shows: implement metadata retrieval, application, and updates in the API and UI. Enhance Show and ShowDto models to include metadata fields, and update the database schema accordingly. Introduce new endpoints for metadata operations and integrate metadata display in the ShowDetail component.

backend/src/TeleWave.Api/Program.cs

@@ -118,6 +118,7 @@ app.MapChannelEndpoints();
 app.MapStreamingEndpoints();
 app.MapMaintenanceEndpoints();
 app.MapSettingsEndpoints();
+app.MapMetadataEndpoints();
 
 // Раздача статики SPA из wwwroot + fallback на index.html для клиентских маршрутов.
 app.UseDefaultFiles();