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/Collections/CollectionErrors.cs

@@ -0,0 +1,21 @@
+using TeleWave.Application.Common.Models;
+
+namespace TeleWave.Application.Library.Collections;
+
+public static class CollectionErrors
+{
+    public static readonly Error NotFound = Error.NotFound(
+        "Collections.NotFound",
+        "Коллекция не найдена."
+    );
+
+    public static readonly Error ShowAlreadyAdded = Error.Conflict(
+        "Collections.ShowAlreadyAdded",
+        "Это шоу уже входит в коллекцию."
+    );
+
+    public static readonly Error ShowNotInCollection = Error.NotFound(
+        "Collections.ShowNotInCollection",
+        "Шоу не входит в коллекцию."
+    );
+}