Commit MWS backend source tree

The ASP.NET Core solution (mws.api/mws.application/mws.domain/
mws.infrastructure) existed only as untracked working files. Adding
it to version control, plus a .gitignore for build output and local
tooling directories, so the CQRS/mediator refactor plan has a real
git history to branch and diff against.

mws.domain/Documents/Document.cs

@@ -0,0 +1,24 @@
+namespace Mws.Domain.Documents;
+
+public enum DocumentType
+{
+    Folder = 1,
+    Document = 2,
+}
+
+public class Document
+{
+    public Guid Id { get; set; }
+    public Guid ProjectId { get; set; }
+    public Guid? ParentId { get; set; }
+    public string Title { get; set; } = string.Empty;
+    public string? Content { get; set; }
+    public DocumentType Type { get; set; } = DocumentType.Document;
+    public Guid CreatedBy { get; set; }
+    public DateTime CreatedAt { get; set; }
+    public Guid? UpdatedBy { get; set; }
+    public DateTime UpdatedAt { get; set; }
+
+    public Document? Parent { get; set; }
+    public List<Document> Children { get; set; } = [];
+}