Update scheduling parameters and refactor channel endpoints: extend HorizonDays to 7 and RetentionDays to 90 in appsettings.json. Consolidate channel-related endpoint logic by removing obsolete files and enhancing the ShowEndpoints with audience and genre management capabilities. Improve error handling and streamline command handlers for channel operations.

backend/src/TeleWave.Application/Library/SetShowGenres/SetShowGenresCommand.cs

@@ -0,0 +1,12 @@
+using LiteCqrs;
+using TeleWave.Application.Common.Models;
+
+namespace TeleWave.Application.Library.SetShowGenres;
+
+/// <summary>Полностью заменяет набор жанров шоу. <paramref name="PrimaryGenreId"/> — какой считать
+/// основным; если он не входит в набор, основным станет первый из списка.</summary>
+public sealed record SetShowGenresCommand(
+    Guid ShowId,
+    IReadOnlyList<Guid> GenreIds,
+    Guid? PrimaryGenreId = null
+) : ICommand<Result>;

backend/src/TeleWave.Application/Library/SetShowGenres/SetShowGenresCommandHandler.cs

@@ -0,0 +1,37 @@
+using LiteCqrs;
+using Microsoft.EntityFrameworkCore;
+using TeleWave.Application.Common.Interfaces;
+using TeleWave.Application.Common.Models;
+using TeleWave.Application.Library.Genres;
+
+namespace TeleWave.Application.Library.SetShowGenres;
+
+public sealed class SetShowGenresCommandHandler(IAppDbContext dbContext)
+    : ICommandHandler<SetShowGenresCommand, Result>
+{
+    public async Task<Result> Handle(
+        SetShowGenresCommand command,
+        CancellationToken cancellationToken
+    )
+    {
+        var show = await dbContext
+            .Shows.Include(s => s.Genres)
+            .FirstOrDefaultAsync(s => s.Id == command.ShowId, cancellationToken);
+        if (show is null)
+            return Result.Failure(ShowErrors.NotFound);
+
+        var ids = command.GenreIds.Distinct().ToList();
+        if (ids.Count > 0)
+        {
+            // Ссылка на несуществующий жанр упала бы нарушением внешнего ключа — проверяем заранее.
+            var known = await dbContext
+                .Genres.Where(g => ids.Contains(g.Id))
+                .CountAsync(cancellationToken);
+            if (known != ids.Count)
+                return Result.Failure(GenreErrors.NotFound);
+        }
+
+        show.SetGenres(ids, command.PrimaryGenreId);
+        return Result.Success();
+    }
+}