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.application/Common/IUnitOfWork.cs

@@ -0,0 +1,14 @@
+using Mws.Application.Common.Repositories;
+
+namespace Mws.Application.Common;
+
+public interface IUnitOfWork
+{
+    IUserRepository Users { get; }
+    IProjectRepository Projects { get; }
+    ITaskRepository Tasks { get; }
+    IDocumentRepository Documents { get; }
+    IRoleRepository Roles { get; }
+
+    Task<int> SaveChangesAsync(CancellationToken ct = default);
+}