Reorganize root folder structure: Remove apps layer layer

backend/src/Modules/Chats/Domain/ChatErrors.cs

@@ -0,0 +1,19 @@
+using Knot.Shared.Kernel;
+
+namespace Knot.Modules.Chats.Domain;
+
+public static class ChatErrors
+{
+    public static readonly Error FileEmpty = new Error("File.Empty", "No file uploaded");
+    public static readonly Error FileInvalidExtension = new Error("File.InvalidExtension", "Must be a ZIP archive");
+    public static readonly Error ImportExpired = new Error("Import.Expired", "Session not found or expired");
+    public static readonly Error ImportMissing = new Error("Import.Missing", "ZIP file lost");
+    public static readonly Error ChatNotFound = new Error("Chat.NotFound", "Chat not found or access denied");
+    public static readonly Error ChatsForbidden = new Error("Chats.Forbidden", "Вы не являетесь участником этого чата.");
+    public static readonly Error MessagesNotFound = new Error("Messages.NotFound", "Message not found.");
+    public static readonly Error ChatsNotFound = new Error("Chats.NotFound", "Чат не найден.");
+    public static readonly Error Unauthorized = new Error("Chats.Unauthorized", "Access denied");
+
+    public static Error ImportCreateChatFailed(string msg) => new Error("Import.CreateChatFailed", msg);
+    public static Error FileTooLarge(int maxMb) => new Error("File.TooLarge", $"File exceeds the maximum allowed size of {maxMb}MB.");
+}